Chapter II: ACROGYNÆ. The apex of the stem or of certain branches is adapted (10)

Order 2. =Saxifragaceæ.= The flowers are 4–5-merous with =2= (-3) carpels, most frequently: S5, P5, A5 + 5 (obdiplostemonous), G2. They are regular, ☿, polypetalous, hypogynous, perigynous or most frequently _more or less epigynous_ (Fig. 488). The carpels may be individually quite free, but are more frequently united at the base, or the entire portion enclosing the ovules is united into a 1- or 2-locular ovary, the styles, however, are always free. _Fruit a capsule_ with many seeds; endosperm present.--They are herbs, most frequently with _scattered_ leaves without stipules; but the leaf-base is broad. The inflorescences are most frequently cymose, and a displacement of the floral-leaves is frequent (_e.g._ _Chrysosplenium_).--~Some _Saxifraga_-species, _e.g._ _S. sarmentosa_, have irregular flower with an _oblique_ plane of symmetry. The petal-stamens in some may be wanting: _Heuchera_, species of _Saxifraga_ and _Mitella_. The corolla is wanting in others.~

_Saxifraga_ (Saxifrage): S5, P5, A5 + 5, G2 (Fig. 488); capsule bilocular, opening along the ventral suture between the 2 persistent styles. ~_S. granulata_ has small tubers at the base of the stem.~--_Chrysosplenium_ (Golden Saxifrage): 4 sepals, _no corolla_, 4 + 4 stamens; 1-locular capsule.

Protandry is most frequently found in _Saxifraga_, with the
stamens successively bending towards the gynœceum; protogyny
is more rare. In other genera there is protogyny without any
movement of the stamens; _Chrysosplenium_ is homogamous.--About
300 species; mostly in temperate climates. _Saxifraga_ is
especially Alpine. _S. crassifolia_ and other species, _Hoteia
japonica_, _Tellima_, etc., are ornamental plants.

The following genera are allied to the Saxifragaceæ:--

=1.= _Parnassia_ (about 14 species; _P. palustris_, Grass of Parnassus). The flower is slightly perigynous, and has S5, P5, 5 fertile sepal-stamens, and 5 petal-stamens, which are developed as barren staminodes, palmately-lobed, and (3–) 4 carpels united in a 1-locular ovary with (3–) 4 parietal placentæ. Capsule.--~Protandrous. The flower has a slightly oblique plane of symmetry, which is especially shown during its development and in the order of sequence in which the anthers dehisce: originally they lie closely round the gynœceum; the anthers dehisce extrorsely, first the one which is placed opposite the most external sepal (the 2/5 arrangement is very distinct in the calyx), the filament elongating so that the anther lies over the ovary, and this is followed successively by the 4 others in a zig-zag line; the filaments bend backwards after the pollen is shed and the anthers drop off, and the stigmas are not developed until this is completed. The barren stamens are palmately divided into an uneven number (7, 9, 11) of lobes, tapering from the centre towards the edge, and bearing apparently glandular tips; their gland-like appearance is supposed to allure flies to visit the flower, or they may act as a kind of fence which compels the insects to enter the flower in a certain way, and thus effect pollination; the honey is secreted on their inner side, and not by the gland-like tips.~

=2.= _Adoxa moschatellina_ (Moschatel). This is a perennial, creeping herb; the horizontal rhizome has an unlimited growth, and bears, in a _scattered_ arrangement, both foliage-leaves, and white, fleshy scale-leaves. The aerial stem bears 2 opposite foliage-leaves and a capitate inflorescence of 5 flowers, 4 placed laterally (in opposite pairs) and 1 terminally. The flower is semi-epigynous, the calyx gamosepalous, corolla absent. The stamens are divided to the base, so that each filament bears a bilocular anther. The style is free, deeply cleft. The _terminal_ flower has 2 bracteoles, 4 sepals, 4 stamens, cleft to the base, and a 4-locular ovary. The bracts of the _lateral_ flowers are displaced on the flower-stalk, as in _Chrysosplenium_, and united with the 2 bracteoles into a kind of 3-leaved involucre; these flowers have 5 sepals, 5 split stamens with 2-locular anthers, and a 5-locular ovary. 1 pendulous ovule in each loculus. Fruit a _drupe_, green-coloured, with 1–5 stones.--This plant, which would perhaps be best placed in a special order, has also been classed with the Araliaceæ and Caprifoliaceæ.

The following are also allied to this order: _Escalloniaceæ_
(arborescent plants with simple, scattered, leathery leaves),
_Cunoniaceæ_ (arborescent with opposite leaves), _Cephalotaceæ_
(with pitcher-like, insect-catching leaves; Australia; Fig.
489) and _Francoaceæ_. These have respectively 85, 107, 1 and 3
species.

FIG. 490.--Floral diagram.

FIG. 491.--Flower in longitudinal section.

FIG. 492.--Seeds in longitudinal section.]

Order 3. =Ribesiaceæ= (=Currants=). 5-stamened Saxifragaceæ with epigynous flowers.--Moderately sized shrubs with _scattered_, stalked and palminerved, and generally palmilobed leaves, with a large leaf-sheath. The flowers (Figs. 490, 491), most frequently borne in _racemes_, are regular, _epigynous_, and have often, _above the ovary_, a cup- or bell-shaped, or tubular prolongation of the receptacle, on which the sepals, petals and stamens are situated; they have 5 sepals (often large, coloured), 5 _small_, free petals, only =5= stamens (opposite the sepals) and a =2=-carpellate gynœceum with a _unilocular_ ovary and 2 _parietal_ placentæ bearing many ovules. The fruit is a _berry_, whose seeds have a fleshy and juicy outer covering (Fig. 492). ~In some species, for example _Ribes grossularia_, there is found an unbranched, or a 3–5-branched spine, very closely resembling the spiny leaves of the _Berberis_, but which, however, are emergences springing from the base of the petiole. _Ribes_ has two kinds of branches: long-branches and dwarf-branches, the latter alone bearing the flowers.~--_Ribes_ (Figs. 490–492). The blades of the leaf are folded or rolled together in vernation. _R. alpinum_ is diœcious.

75 species; especially from the N. Temp. regions (especially
N. Am.).--The receptacle secretes honey on its inner surface.
The Gooseberry-flower is slightly protandrous, others are
homogamous; insect-and self-pollination are found. The following
are FRUIT BUSHES: _R. nigrum_ (Black Currant), _R. rubrum_
(Red Currant), _R. grossularia_ (Gooseberry), originating in
Northern Europe and Asia. ORNAMENTAL BUSHES: the North American
_R. aureum_ (Golden Currant) and _R. sanguineum_ (Blood-red
Currant), etc.

Order 4. =Hydrangeaceæ.= Shrubs, with simple, opposite leaves, without stipules; flowers generally epigynous, 4–5-merous (Fig. 493).--_Hydrangea_ (_H. hortensia_, etc.). Shrubs from N. Am. and E. Asia; corolla often valvate. The inflorescence, as in the case of the inflorescence of _Viburnum opulus_ (Guelder Rose), has often irregular, large, but barren flowers at the circumference, whilst the others are much smaller, regular and ☿; the barren flowers are mostly 4-merous; in these cases it is the calyx which is large and petaloid, while the other parts of the flower are more or less suppressed. The branches of the inflorescence appear to be partially devoid of floral-leaves, since they are displaced upon the main axis.--_Philadelphus_; racemes (with terminal flower), sepals 4 (valvate), petals 4 (twisted), stamens many, and carpels 4 (opposite the petals), forming a 4-locular ovary. The numerous stamens (20–30) occur by the splitting of the sepal-stamens and are often therefore placed in distinct bundles. Fruit a capsule. _Ph. coronaria_ (Syringa, Mock Orange-blossom), from S. Eur., is a common ornamental shrub, as also is _Deutzia_ (Fig. 493) from N. Am. and E. Asia. The latter has S5, P5, A5 + 5, G3.--About 70 species.

Order 5 (?). =Pittosporaceæ.= This order has its home especially in Australia (90 species). The flower has S5, P5, A5 (episepalous), G2 (3–5), most frequently a unilocular ovary with many ovules in 2 rows, borne on 2 parietal placentæ, or a bilocular ovary. Some have berries, others capsules. _Pittosporum, Citriobatus, Sollya, Billardiera._

Order 6. =Hamamelidaceæ.= Flowers more or less epigynous, with S4, P0 or 4, 4 fertile sepal-stamens, and 4 barren petal-stamens, bilocular ovary with 1–2 ovules in each loculus. Fruit a capsule. _Hamamelis_: one species in Japan and one in N. Am. _Fothergilla._ _Liquidambar_: monœcious; flowers in capitula or spikes; ♂-flowers without perianth, stamens indefinite; ♀-flower: slight perianth, 2-locular ovary with many ovules. OFFICINAL: “Styrax-balsam,” which is obtained by boiling the bark of _Liq. orientalis_, from Asia Minor. _Liquidambar_ and _Parrotia_ are found as fossils in the Upper Oligocene; _Hamamelis_ perhaps in the Chalk.

Finally two orders with very reduced flowers are included in this family.

Order 7. =Platanaceæ.= Trees, with large, scattered, palminerved and lobed leaves, and ochreate stipules; the buds are concealed in a hollow at the base of the petiole. The bark falls off in large scales. ♂-and ♀-flowers (monœcious) in crowded, spherical inflorescences which are placed at wide intervals on a terminal, thin, and pendulous axis. The flowers have an insignificant calyx and corolla; the ♂-flower has few stamens; ♀-flower, perigynous, with 4 free carpels, 1 _pendulous_, _orthotropous_ ovule in each. Fruit a nut; endosperm absent. 5 species; frequently grown in avenues and parks. _P. occidentalis_ (N. Am.); _P. orientalis_ (W. Asia.).

Order 8. =Podostemaceæ.= Aquatic plants, especially in swiftly running water, with somewhat of an Alga-like, Moss-like, or thalloid appearance; they show themselves in many ways to be adapted to their mode of life and situations (having a dorsiventral creeping stem, the flowers sunk in hollows, a formation of haptera upon the roots, and thalloid assimilating roots and thalloid stems, etc.). Tropical; 100 species.

Family 20. =Rosifloræ.=

The leaves are scattered, stipulate, or have at least a well developed sheath, which is generally prolonged on each side into a free portion (“adnate stipules”). The flowers are regular, _perigynous_ or _epigynous_. Calyx and corolla 5 (-4)-_merous_ with the usual position. The corolla is always polypetalous. The stamens are present in very varying numbers (5–∞) and position, but _always_ placed in 5-_or_ 10-_merous whorls_; they _are frequently_ 20 in 3 whorls (10 + 5 + 5; see Figs. 494, 502, 505); the nearer they are placed to the circumference, the longer they are; they are generally _incurved in the bud, or even rolled up_. The number of the carpels is from 1–∞; in most cases all are _individually free_ (syncarp), and when they are united it is in every case with the ovaries only, whilst the _styles_ remain more or less _free_ (_Pomaceæ_, species of _Spiræa_). The _seeds_ have a straight embryo, and usually no endosperm.

The perianth and stamens are most frequently _perigynous_ on
the edge of the widened receptacle; its form varies between a
flat cupule and a long tube or a cup (Figs. 495, 496, 498, 499,
500); the carpels are situated on its base or inner surface, in
some instances on a central conical elongation of the floral
axis (Fig. 496). The carpels in _Pomaceæ_ also unite more or
less with the hollow receptacle, or this grows in and fills up
the space between the carpels, so that a more or less epigynous
flower is formed (Fig. 504).--The following numbers of _stamens_
occur: 5, 10 (in 1 whorl), 15 (10 + 5), 20 (10 + 5 + 5), 25 (10
+ 10 + 5), 30-50 (in 10-merous whorls)--compare the diagrams.
The theoretical explanation of this relation of the 10-merous
whorls and their alternation with the 5-merous whorls is not
definitely determined; a splitting of the members of the
5-merous whorls may be supposed, but the development shows no
indication of this, and it is not supported in any other way.
Several genera have “_gynobasic_” styles, that is, the style
springs from the base of the ovary (Fig. 497 _A_, _B_).

The Rosifloræ are on one side closely related to the
Saxifragaceæ (especially through _Spiræa_) from which it is
difficult to separate them, and to the Myrtifloræ; on the other
side they are allied, through the Mimosaceæ with the large
number of stamens, and through the Amygdalaceæ with its single
carpel, to the Leguminosæ. The family begins with forms which
have many-seeded follicles, and passes on the one side to forms
with nuts and drupes in perigynous flowers, and on the other
side to the Pomaceæ.

Order 1. =Rosaceæ.= Herbs or shrubs, generally with compound leaves and persistent (adnate) stipules, flower _perigynous_, _gynœceum formed of many free_ (therefore oblique) _carpels, syncarps_ with fruitlets of various kinds. The exceptions are noted under the genera.

=1.= SPIRÆEÆ (Fig. 495) has 2–many ovules in each ovary, while in the other groups there is generally only 1, and never more than 2 ovules in each loculus. There are generally 5 _cyclic_ carpels and the fruit is 5 _follicles_, which are not enclosed by the receptacle. The majority are shrubs. Stipules are often wanting.--_Spiræa_ (Meadow-Sweet). The flowers are generally borne in richly flowered inflorescences of various forms. The carpels, in some species, unite together and form a _simple_ gynœceum with free styles (an approach to the _Pomaceæ_).--~Closely allied to _Spiræa_ are the East Asiatic shrubs: _Kerria japonica_, which has solitary flowers, in this country nearly always double (the fruit a nut), and _Rhodotypos kerrioides_ which has opposite leaves, a remarkable feature among the Rosifloræ; it has a 4-merous flower, a well developed disc inside the andrœcium, and a drupe. Closely allied also is _Gillenia_ (N. Am.) differing chiefly in the ascending ovules, _Spiræa_ having pendulous ovules, and a more tubular receptacle.~

The groups _Quillajeæ_ and _Neuradeæ_ form a transition from
_Spiræa_ to _Pomaceæ_. In the first group, which contains only
trees or shrubs with generally simple leaves, the carpels are
either free or united (into a capsule); in the second the
receptacle unites with the carpels, which are themselves often
united together; in this case, too, the fruit is a capsule.
_Quillaja_ (S. Am.); _Exochorda_ (China).

=2.= POTENTILLEÆ (Figs. 494, 496, 497). The flower has an “_epicalyx_” (Fig. 494 _C_) alternating with the sepals and formed by their stipules which are united in pairs, and hence its leaves are often more or less deeply bifid. The receptacle is cupular and often quite insignificant. The sepals are valvate in the bud. The large number of fruitlets are _achenes_, borne on a well-developed convex portion of the receptacle (~the Ranunculeæ resemble the Potentilleæ, but have no epicalyx, no enlarged receptacle, and spirally-placed stamens~). Most of the species are herbs with dichasial inflorescences, often arranged in racemes.--_Potentilla_ (Cinquefoil). The achenes are borne on a _dry_, hairy receptacle; the style is situated towards the apex of the ovary, and is not prolonged after flowering. Herbs with digitate, in some, however, pinnate leaves, and generally yellow flowers.--_Comarum_ (Fig. 494) (Marsh Cinquefoil) forms, by its fleshy-spongy receptacle, a transition to the next genus.--_Fragaria_ (Strawberry) (Fig. 496). The receptacle becomes finally fleshy, coloured, and falls off (biologically it is a berry); the numerous fruitlets (drupes with thin pericarp) have basal styles (Fig. 497); leaves trifoliate; long, creeping runners.--_Geum_ (Avens) has a terminal style which after flowering elongates into a long beak, with the apex (after the uppermost part has been thrown off) bent back into a hook, thus furnishing a means of distribution for the fruits. Leaves pinnate.--~_Dryas_ comprises 3 Arctic or Alpine species with simple leaves and solitary flowers, the calyx and corolla 8–9-merous, the fruit resembles that of _Geum_, but the styles become still longer and feather-like (a flying apparatus).~

FIG. 496.--Longitudinal section of flower.

FIG. 497.--A carpel, entire, and in longitudinal section.]

=3.= RUBEÆ. _Rubus_ (Bramble) has the same form of receptacle as the _Potentilleæ_, but _no epicalyx_; _the fruitlets are drupes_, not enclosed by the persistent calyx. Most frequently shrubs or undershrubs with prickles (emergences), glandular bristles and compound leaves. In the Raspberry (_R. idæus_) the fruitlets unite together and detach themselves from the receptacle.

=4.= ROSEÆ. _Rosa_; the receptacle is hollow, ovoid and contracted beneath the insertion of the calyx (Fig. 498), ultimately _fleshy_ and _coloured_; it encloses a large number of fruitlets which are achenes as hard as stones (“hip,” biologically a berry).--Shrubs with imparipinnate leaves and adnate stipules. ~The sepals show clearly the order of their development (a divergence of 2/5), the two outer ones on both sides are lobed, the third one on one side only, and the two last, whose edges are covered by the others, are not lobed at all. _Prickles_ (emergences) are generally present and in some species are placed in regular order, being found immediately below each leaf (usually two) although at somewhat varying heights.~

FIG. 499.--Flower in longitudinal section.

FIG. 500.--Fruit and receptacle in longitudinal section.]

=5.= AGRIMONIEÆ. The receptacle is more or less cup- or bell-shaped, and almost closed at the mouth; it is persistent and envelopes the _nut-like fruitlets_, but is _dry_, and in some species hard, the fruitlets being firmly attached to it. In biological connection with this the number of the carpels is generally only 1 or 2, and the whole becomes a _false nut_ (Fig. 500). Herbs.--_Agrimonia_ (Agrimony; Figs. 499, 500); the perianth is 5-merous, stamens 5–20. The receptacle bears externally, on the upper surface, a number of hooked bristles which serve as a means of distribution for the 1–2 achenes which are enclosed in it, and hence the entire flower finally falls off. The inflorescence is a long upright raceme. ~These bristles are arranged in whorls of 5 and 10, of which the uppermost alternate with the sepals.~--_Alchemilla_ (Ladies-mantle; Fig. 501) has 8 green perianth-leaves in two whorls (some authorities consider the four outer as an epicalyx, and the flower therefore apetalous), and 4 stamens _alternating with the innermost whorl_. There is only one carpel with a _basal_ style and capitate stigma. The flowers are small and greenish, the filaments jointed. The anthers open by one extrorse cleft. The leaf-sheath entirely envelops the stem; the leaves are palminerved. _A. aphanes_ has often only 1–2 stamens. ~The following genera, with 4-merous flowers borne in short spikes or capitula, are allied to this group. _Sanguisorba_ has entomophilous, ☿-flowers with 4(-20) stamens, 1 carpel; stigma papillose.--_Poterium_; spike or capitulum, the uppermost flowers are ♀, the lowermost ♂, and some intermediate ones ☿ (the order of opening is not always centripetal); S4, P0, A20–30, G2, the long styles having brush-like stigmas (wind-pollination). Leaves imparipinnate.~

POLLINATION. A yellow ring on the inner side of the receptacle,
inside the stamens, serves as a nectary when any honey
is formed; this, for instance, is not the case in _Rosa,
Agrimonia_, _Spiræa ulmaria_, _S. filipendula_, _S. aruncus_,
etc., to which the insects (especially flies and bees) are
allured by the quantity of pollen. Homogamy and slight
protogyny are frequent, in many instances self-pollination
also is finally possible. _Poterium_, with the long-haired
stigma, is wind-pollinated.--About 550 (1100?) species,
especially in northern temperate regions.--USES. OFFICINAL:
the petals of _Rosa centifolia_ and _gallica_, the fruits of
the Raspberry (_Rubus idæus_), the rhizome of _Geum urbanum_,
the flowers of the Koso-tree (_Hagenia abyssinica_ or _Brayera
anthelmintica_).--The bark of _Quillaja saponaria_ (Chili) is
used as soap and contains _saponin_. “Attar of Roses” from
_Rosa damascena_, _centifolia_ and other species, especially
from the southern slopes of the Balkans. Many species and
varieties of Roses are ORNAMENTAL plants: from S. Europe, _Rosa
lutea_ (the Yellow Rose), _R. gallica_ (the French Rose) and
_R. rubrifolia_; from W. Asia, _R. centifolia_, of which the
Moss Roses (_R. muscosa_ and _cristata_) are varieties, and _R.
damascena_; from India and N. Africa, _R. moschata_ (the Musk
Rose); from China, _R. indica_ (Tea Rose) etc., besides the
native species and the varieties which have been derived from
them. In addition, _Kerria japonica_, species of _Potentilla_,
_Rubus odoratus_ from N. Am., and many species of _Spiræa_ from
South-eastern Europe and N. Am. ESCULENT: the “hips” of _R.
mollissima_, _R. pomifera_, etc.; the fruits of _Rubus_-species:
Raspberry (_R. idæus_), Cloudberry (_R. chamæmorus_), Blackberry
(_R. fruticosus_), etc.; of _Fragaria_-species (_F. vesca_,
_collina_, _grandiflora_, etc).

Order 2. =Amygdalaceæ.= Trees or shrubs with rosaceous flowers; leaves simple with caducous stipules; a regular, _perigynous_ flower, the receptacle being partly thrown off by a circular slit; sepals 5, petals 5, stamens 20–30; _gynœceum simple, formed of 1 carpel_ (hence oblique, Fig. 502), with terminal style and 2 pendulous ovules, ripening into a _drupe_ (Fig. 503).--The leaves are penninerved and frequently have _glands_ on the stalks and edges; _thorns_ (modified branches) often occur, _i.e._ dwarf-branches, which, after producing a few leaves, terminate their growth in a thorn (_e.g._ _Prunus spinosa_). ~The vernation of the _foliage-leaves_ varies in the different genera; in the Almond, Peach, Cherry, and Bird-Cherry they are folded; in the Apricot, Plum, Sloe and Bullace, rolled together. In some the flowers unfold before the leaves (_Amygdalus_, _Armeniaca_). That the gynœceum is formed of 1 carpel is evident in this as in other instances (_e.g._ in the Leguminosæ, which are closely related to this order), from the fact that the carpel is oblique, and has only one plane of symmetry, and similarly in the fruit there is a longitudinal groove on one side which indicates the ventral suture. It is only exceptionally that both ovules are developed. In abnormal instances more than 1 carpel is developed.~

=A.= FRUIT HAIRY: _Amygdalus_ (_A. communis_, Almond-tree) has a dry pulp which is detached irregularly, when ripe, from the wrinkled, grooved, ovoid and somewhat compressed stone.--_Persica_ (_P. vulgaris_, Peach-tree) differs from the Almond in having a juicy pulp, not detachable from the stone, which is deeply grooved and has pits in the grooves (Fig. 503). (~The name of the genus is derived from Persia, though it is a native of China.~).--_Armeniaca_ (_A. vulgaris_, Apricot) has a hairy, velvety fruit, but the stone is smooth and has two ribs along one of the edges; the pulp is juicy. (~The generic name has been given on the incorrect assumption that it was a native of Armenia; its home is China.~)

=B.= FRUIT GLABROUS (_i.e._ without hairs): _Prunus_ (Plum) has a glabrous fruit with bluish bloom; the stone is compressed, smooth or wrinkled. The flowers are borne solitarily or in couples, and open before or at the same time as the leaves; they are borne on shoots without foliage-leaves.--_Cerasus_ (Cherry) has a glabrous, spherical fruit, without bloom, and a spherical stone. The flowers are situated in 2–many-flowered umbels or racemes, and open at the same time as the leaves or a little before them. ~_Long-stalked_ flowers in _umbels_ are found in _C. avium_ (Wild Cherry), _C. vulgaris_ (the cultivated Cherry, from Western Asia); _racemes_ at the apex of leaf-bearing branches and small spherical fruits are found in _C. padus_ (Bird Cherry), _C. virginiana_, _C. laurocerasus_ (Cherry-laurel), _C. mahaleb_.~

POLLINATION. _Prunus spinosa_ (Sloe, Blackthorn) is protogynous,
but the stamens are developed before the stigma withers. Honey
is secreted by the receptacle. _Cerasus padus_ (Bird-Cherry)
agrees in some measure with _P. spinosa_. In the flowers of
the Plum and Cherry the stamens and stigma are developed
simultaneously and self pollination seems general; the
stigma, however, overtops the inner stamens and thus promotes
cross-pollination.--DISTRIBUTION. 114 species in the N. Temp,
zone; few in the warmer regions; the majority from W. Asia. _C.
vulgaris_, from the regions of the Caspian; _Prunus spinosa_,
_insititia_ (Bullace), _domestica_ (Plum, from the Caucasus,
Persia).--USES, principally as fruit-trees: Cherry, Plum,
Apricot, etc.; “Almonds” are the seeds of _Amygdalus communis_
(W. Mediterranean), “bitter,” “sweet,” and “shell” almonds are
from different varieties, the latter being remarkable for the
thin, brittle stone. In the majority of species and in almost
all parts of the plant (especially the bark, seed and leaves)
is found the glycoside, _amygdalin_, which forms prussic acid.
Many form _gum_, and the seeds have _fatty oils_ (“Almond
oil”). OFFICINAL: the seeds and oil of _Amygdalus communis_,
and the fruit of the Cherry; in other countries also the leaves
of _C. laurocerasus_.--The stems of _Cerasus mahaleb_ are
used for pipes. Ornamental Shrubs: _Amygdalus nana_, _Cerasus
laurocerasus_.

Order 3. _Chrysobalanaceæ._ Tropical Amygdalaceæ with
zygomorphic flower and gynobasic style. 200 species; especially
Am. and Asia. _Chrysobalanus icaco_ (Cocoa-plum) is cultivated
on account of its fruit (Am.)

Order 4. =Pomaceæ.= Trees and shrubs, most frequently with simple leaves and caducous stipules. The flowers (Fig. 505) have 5 sepals, 5 petals and generally 20 stamens (10 + 5 + 5, or 10 + 10 + 5). There are from 1–5 _carpels_, which unite entirely or to some extent with each other, and with the hollow, fleshy receptacle (the _flower_ becoming _epigynous_), (Figs. 505, 506, 507). The carpels are nearly always free on the ventral sutures, rarely free at the sides also. The whole outer portion of the fruit becomes fleshy, but the portions of the pericarp surrounding the loculi (endocarp) are most frequently formed of sclerenchymatous cells, and are more or less firm (the “core”). The nature of the fruit varies, according to the thickness and hardness of the endocarp, being either a “berry” or a “drupe” (see _A_ and _B_). When the endocarp is thin and parchment-like, the fruit has the characteristics of a berry, each of the 5 loculi generally present containing several seeds; but when this is hard the fruit resembles a drupe, only one seed is developed in each loculus, and the number of the loculi is reduced to one or two. There are nearly always 2 ovules in the loculi of the ovary, but in _Cydonia_ there are a large number in 2 rows. In the genera which have stones, only one seed is developed in each stone. The genera are distinguished mainly in accordance with the kind of fruit and the number of ovules and seeds.

=A.= SORBEÆ. THE ENDOCARP IS PARCHMENT-LIKE OR PAPERY (drupe, with thin stone or berry).

1. _Pyrus_ and _Cydonia_; carpels completely embedded in the cup-like receptacle, styles always free.--_Pyrus_: the fruit is glabrous, and has only a small calyx, withering or deciduous, and a 5-locular ovary with at most 2 ascending ovules in each loculus (Fig. 504 _D_). The large flowers are situated in few-flowered umbels or corymbs. ~_P. communis_ (Pear; free styles, Fig. 507; it has the well-known pear-shaped fruit; the core is reduced to several groups of sclerenchymatous cells embedded in the pulp, the leaf-stalk is as long as the blade).~--_Cydonia_ (Quince) has a hairy fruit with _many seeds in 2 rows_ in each loculus of the endocarp (Figs. 504 _C_, _F_; 506); the testa of these seeds is mucilaginous. _C. vulgaris_, large, terminal flowers on lateral branches, and large leaf-like, persistent sepals.

2. _Malus_ and _Amelanchier_ (_Aronia_); carpels free on the ventral edge; styles united. _Malus communis_ (Apple) the fruit is “umbilicate” at the base; no sclerenchymatous cells in the pulp; styles united at the base (Fig. 504 _D_); leaf-stalk shorter than the blade. _Sorbus_ (Mountain-ash) differs only in having a 2–3-locular fruit with extremely thin endocarp. Cymose inflorescences in umbellate cymes. ~_S. aucuparia_ has pinnate leaves, _S. aria_ (White-beam) and other species have simple leaves.--_Amelanchier_ (the Service-tree) has a false divisional wall springing from the dorsal suture, and more or less projecting into each of the loculi of the ovary; _Raphiolepis_ (Fig. 504 _E_) has racemes and a juicy berry; _Eriobotrya japonica_ (Loquat).~

=B.= CRATÆGEÆ. THE ENDOCARP IS HARD AND BONY (“drupes,” generally with several, sometimes, however, with only 1–2 stones, rarely one multilocular stone; only 1 seed in each of the loculi).--_Cratægus_ (Hawthorn, May). There are 1–5 stones in the spherical or ovoid fruit. The disc, found on the apex of the fruit, inside the small, withered calyx, is small (much less than the transverse section of the fruit). Shrubs with thorns (branches) and moderately large flowers borne in corymbs.--_Mespilus_ (Medlar) differs from the last-named only in having a _large disc_ at the apex of the fruit, inside the large, _leaf-like sepals_, _i.e._ almost equal to the greatest diameter of the fruit. The flowers are solitary and terminal.--_Cotoneaster_ is chiefly distinguished from the others by its syncarps, the 2–5 carpels (and stones) being free from one another, and only united to the receptacle by a larger or smaller portion of their dorsal surface (Figs. 504 _A_, _B_). Small shrubs with leathery leaves, generally covered with white, felted hairs on the lower surface, and with small flowers; the fruit is red or black.

Pear, Apple, Mountain Ash and Hawthorn have protogynous
flowers which secrete honey, and are conspicuous to ensure
insect pollination.--180 species; in the northern temperate
regions.--Pear and Apple are especially cultivated as fruit
trees in a number of varieties; the Paradise Apple (_Pyrus
baccata_); especially in southern countries also the Quince
(from N. Persia and the Caucasian districts), Medlar and
_Amelanchier vulgaris_. _Malus pumila_ (Caucasus,
Altai) and _M. dasyphylla_ (Orient, S. Eur.) are regarded
as primitive forms of the Apple-tree; _M. sylvestris_,
which grows wild in European forests, appears to have been less
used. The early Lake-dwellers in Switzerland had the apple-tree
both wild and cultivated.--The original form of the Pear is
supposed to be _Pyrus achras_ (Central Asia).--Many of
the species of _Cratægus_, some with double flowers, and
_Pyrus (Chænomeles) japonica_, with brilliant red flowers,
are cultivated as ornamental shrubs. OFFICINAL: Quince
pips, on account of the mucilaginous testa.--The fruits contain
free organic acids and sugar; prussic acid may be obtained from
the seeds. The wood of the Pear-tree is used in manufactures.

Family 21. =Leguminosæ.=

The most characteristic feature is, that the _gynœceum is 1-locular_ and formed of _1 carpel, the ventral suture of which is turned posteriorly_. The fruit, in most instances, is a _pod_ (legume), which opens generally along both sutures, the two valves twisting more or less in opposite directions. ~In other instances it opens along one suture only, or as a pyxidium (Red Clover), or it is indehiscent, in which case it is more or less berry-like (_e.g._ the Tamarind, Carob-bean), or it is a drupe (_e.g._ the Tonquin-bean), or a 1–few-seeded nut (_e.g._ _Melilotus_), or a lomentum, which divides transversely into as many joints as there are seeds (_Ornithopus_, see Fig. 513).~

The inflorescences belong to the _centripetal_ type (_i.e._ indefinite); cymes do not occur. The flowers are _zygomorphic_, with vertical plane of symmetry, seldom regular; _5-merous_ with but a few exceptions, ☿, and slightly _perigynous_. The following diagram is the most general (Fig. 511): 5 sepals, with the _unpaired sepal median and anterior_, 5 petals, 5 + 5 stamens, all in alternating whorls, 1 carpel. The calyx is most frequently gamosepalous, the gynœceum is narrowed down at the base to a short stalk and, in the majority, is more or less bent. The seed is most frequently kidney-shaped, with a smooth, hard and shining testa, the hilum being very distinct. _Endosperm is wanting_, or is reduced to a thin layer, which is of service when the seed swells during germination. The vegetative parts have these features in common, namely, the _leaves are scattered, stipulate_, and almost always _compound_. Peculiar _sleep-movements_ and _sensitiveness_ are found in some, chiefly in the Mimosas. Many, probably all, Leguminosæ have _small tubercles on their roots_ which are produced by a kind of bacterium, and assist in the assimilation of free nitrogen. Spontaneous movements are exhibited by _Desmodium gyrans_ (Telegraph-plant).

This family is closely allied to the Rosifloræ, with which it
agrees in the scattered leaves, the presence of stipules, the
generally 5-merous and most frequently perigynous flowers with
eucyclic stamens, and the absence of endosperm. _Amygdalaceæ_
and _Chrysobalanaceæ_, with solitary carpels, approach on one
side to the Leguminosæ, among which genera with drupes are also
found; _Mimosaceæ_, with their many stamens, form a connecting
link on the other side. In this respect the Mimosa-genus
_Affonsea_, and certain Cæsalpineæ and Swartzieæ, are of special
interest in having more than one carpel (syncarp), a condition
which is sometimes met with abnormally in other Leguminosæ, as
well as in Amygdalaceæ. About 7,000 species of the Leguminosæ
are known.

Order 1. =Cæsalpiniaceæ.= These are _leguminous plants with straight embryo and a flower which is not papilionaceous and has not the same æstivation_ (Figs. 508–510); but in reality there is not a single characteristic which absolutely distinguishes them from the Papilionaceæ.--The majority are arborescent; the leaves as a rule are pinnate or bipinnate. The flower is 5-merous, most frequently perigynous and slightly zygomorphic; the calyx is free or gamosepalous, the corolla polypetalous with _ascending imbricate æstivation_ (_i.e._ the two lowest petals envelop the lateral ones, and these again the posterior; Fig. 508); 10 _free stamens_; fruit various.

FIG. 508.--Floral diagram.

FIG. 509.--Flower.

FIG. 510.--The same in long. sect.]

_Cassia_ (Figs. 508–510) is the largest genus (about 200 species); it has an almost hypogynous, zygomorphic flower with 5 free sepals and petals; of the 10 stamens the 3 posterior are generally barren, the others are of very unequal length and open at the apex by _pores_ (Fig. 509). In some (the _Senna_ group) the fruit is a flat, short, thin, dehiscing pod; in others (_Cathartocarpus_) it is round, long, woody or fleshy, indehiscent, and divided internally by more or less fleshy transverse walls into as many cells as there are seeds.--The following also have DEHISCENT FRUITS: _Bauhinia_ (often lianes, tropical climbers with tendrils [stem-structures] and anomalous stems), _Copaifera_, _Hæmatoxylon_ (whose pod does not dehisce along the suture, but laterally), _Cercis_ (simple leaves; the corolla resembles that of the Papilionaceæ, but the posterior petal is the smallest, and is enveloped by the 2 lateral ones, which are enveloped in their turn by the 2 anterior).--FRUIT INDEHISCENT: _Tamarindus indica_; the pod is almost round, often a little abstricted between the seeds; the wall is formed by a thin, brittle external layer, enclosing an acid pulp; well-developed septa are present, between the seeds; the most internal layer is parchment-like. Calyx 4-merous by the coalescence of 2 sepals. Only 3 fertile stamens.--_Ceratonia siliqua_ (Carob-bean, Locusts); the pod is long, compressed, with thick sutures, and has a wall, the central part of which is more or less leathery, fleshy and sweet; there are transverse septa between the seeds, as in the Tamarind. Embryo greenish in endosperm. The flower is without a corolla, 5 stamens.--_Pterogyne_ (winged fruit), etc.--KRAMERIEÆ with _Krameria_ is an anomalous group.

DISTRIBUTION. 80 genera, with 740 species; almost exclusively
in the Tropics. The Carob-tree and _Cercis_ grow in the
Mediterranean basin. The largest and most widely distributed
genus is _Cassia_, which is found as trees, shrubs, and weeds
in all tropical countries. The order has many important
uses to mankind. MEDICINAL: the leaves and pods of _Cassia
acutifolia_ and _angustifolia_ (officinal, Senna-leaves),
the fruit-pulp of the _Cassia_-sub-genus, _Cathartocarpus_.
Rhatany root from _Krameria triandra_ (Peru, officinal).
_Balsam_ is extracted from a number of _Copaifera_-species
(Balsam of Copaiba) from S. Am. (officinal), and from _Hymenæa_
(Copal balsam), _Trachylobium_ and others. _Edible fruits_ are
obtained especially from the Carob-tree (from the East) and
the Tamarind (officinal). The heart-wood of several species of
_Cæsalpinia_, such as _C. brasiliensis_ (the Pernambuco-tree),
_echinata_ (Red-tree), and _sappan_, yield _dyes_; _Hæmatoxylon_
(_H. campechianum_, Logwood), _Copaifera bracteata_
(Amarant-tree).--_Timber_ is obtained from many (_Melanoxylon_
and others). In Europe they are of little importance as
ornamental plants, these being confined principally to the
species of _Gleditschia_ (_G. triacantha_, from N. Am.) and
_Cercis_ (the Judas-tree, _C. siliquastrum_, S. Eur.), which
are cultivated in gardens; but in tropical gardens beautiful
flowering species, _e.g._ of _Cassia_, _Poinciana_, _Brownea_,
are found, and the most beautiful of all ornamental plants, the
Indian _Amherstia nobilis_.

Order 2. =Papilionaceæ.= The flower (Figs. 511, 512) is _strongly zygomorphic_ and somewhat perigynous (Fig. 512 _B_; most frequently more on one side than the other). The calyx is _gamosepalous_ and persistent. The polypetalous corolla has _descending_ imbricate æstivation, the posterior, large leaf, the _standard_ (Figs. 511 _f_; 512 _B’_, _e_), _covering in the bud_ the two lateral ones, the _wings_ (Figs. 511 _v_; 512 _B’_, _a_), which again cover the two anterior; these are united in the form of a boat, the _keel_ (_k_ and _c_); the wings and the two petals of the keel are very unsymmetrical. That the keel is formed of two petals is seen by its position (in front of one sepal) and by the two often more or less free claws. The 10 (5 + 5) _stamens_ (monadelphous) _are either all united into one bundle, or into two bundles_ (diadelphous), the posterior one being free (Fig. 512 _C_). The ovules are _curved_ and _also the embryo_ (Fig. 512 _G_), especially the hypocotyl, so that the radicle assumes a position close to the edge of the thick, fleshy cotyledons. Endosperm wanting; the cotyledons are very rich in proteid reserve material. The forms of the fruit and exceptions are described under the genera.

_Geocarpic_ fruits, _i.e._ those which penetrate the soil during
their development and ripen underground, are found in _e.g._
_Arachis hypogæa_ (see page 472), _Trifolium subterraneum_,
_Vicia amphicarpæa_. _Germination_ takes place in various ways.
In the majority the cotyledons are raised above the ground as
green, leaf-like bodies; in the Vicieæ they remain thick and
white, and are always enclosed in the testa, and are therefore
never able to take part in the work of assimilation; in species
of _Phaseolus_, on the other hand, they are raised well above
the ground and become green, but remain however thick and fleshy.

=1, 2.= The two groups PODALYRIEÆ (the majority of the genera
are Australian) and SOPHOREÆ (_Sophora_, _Edwardsia_, etc.),
represent the oldest type, as they have 10 _free stamens_ and so
form the transition to the Cæsalpiniaceæ. Nearly all are trees
and shrubs.

=3.= ASTRAGALEÆ. Herbs or shrubs, less frequently trees, with _imparipinnate_ leaves (without tendrils). The flowers are generally borne in racemes or spikes. Stamens monadelphous or diadelphous.--_Astragalus_ (Milk-Vetch) has the legume incompletely divided longitudinally into 2 loculi by a septum formed by the incurved dorsal suture. Diadelphous.--_Glycyrrhiza_ (Liquorice); _Colutea_ (Bladder-Senna) from S. Europe; _Robinia_ (the false Acacia) with thorny stipules; _Indigofera_ (the Indigo plant); _Amorpha_ (which has only one petal, namely the standard, and the fruit a nut), _Caragana_, _Wistaria_ (a climbing shrub), _Galega_. _Carmichælia australis_, when old, produces flat branches with scale-like leaves.

=4.= VICIEÆ. _Climbing herbs_ with _paripinnate_ leaves, the midrib ending in a point or frequently in a _tendril_, which generally is branched, representing lateral veins without mesophyll; stamens diadelphous; the cotyledons remain underground on germination.--_Vicia_ (Vetch) has a filamentous style, hairy towards the tip, and a pod with many seeds; climbing by means of tendrils; the leaves have many leaflets.--_Faba_ (_F. vulgaris_, Horse-bean) is erect, without tendrils; its pod is thick with spongy septa between the seeds.--_Ervum_ (Lentil) has a pod with only 1–2 seeds, and sweeping hairs (stylar-brush) on the inner side of the style.--_Pisum_ (Pea; Fig. 512) has very large stipules, the bent style has a hollow groove on the anterior side. _P. sativum_ (Common Pea), _P. arvense_ (Grey Pea).--_Lathyrus_ (Sweet Pea) generally has an angular, winged stem and most frequently only a few pairs of leaflets. The style is flattened, with sweeping hairs on the back. ~In _L. aphaca_ the stipules alone are developed into foliage-leaves, while the remainder of the leaf is modified into a tendril.~--_Cicer_ has a nearly straight embryo and imparipinnate leaves with dentate or incised leaflets. _C. arietinus_ (Chick-pea).--~_Abrus_ (_precatorius_, etc.); the seeds (“Crab’s eyes,” “Paternoster peas,” “Jequirity”) are scarlet with a black spot round the hilum.~

=5.= PHASEOLEÆ. Herbs, twining or erect, but not climbing by tendrils; the leaves are imparipinnate, generally _ternate_, and bear small, linear bodies resembling stipules at the base of the stalks of the leaflets. The inflorescences are most frequently compound, groups of few flowers being situated on short, nodose, lateral axes borne on a longer stem. On germination the cotyledons are raised a considerable distance above the ground, and become greenish, but do not become leaf-like; in _P. multiflorus_ they remain underground. Stamens as in the Vetches.--_Phaseolus_ (Kidney-bean): the keel with the stamen and style is spirally _twisted_ (to the right). Herbs, twining to the left.--~The “Calabar-bean” (_Physostigma venenosum_), _Erythrina_, _Clitoria_, _Glycine_, _Soja_, _Mucuna_, _Apios_, _Canavalia_, _Vigna_, _Dolichos_, _Cajanus_, _Rhynchosia_, etc.~

=6.= TRIFOLIEÆ (CLOVERS). Herbs with _ternate_ leaves, the leaflets are often dentate with the veins prolonged into the teeth; stamens diadelphous; fruit 1-locular, 1–few-seeded, pyxidium-like, irregularly dehiscent, or more frequently a _nut_. The flowers are generally borne in capitula, racemes, or spikes.--_Trifolium_ (Clover). The corolla is gamopetalous. The calyx persists, together with the corolla, round the ripe fruit. The inflorescence is a spike, capitulum or capitate umbel; the leaves are ternate, and have adnate stipules.--_Medicago_ (Medick). The corolla falls off after flowering; fruit curved like a sickle or spirally twisted; it is a nut, and opens with difficulty. Leaves ternate.--_Melilotus_ (Melilot) has a small, spherical or lanceolate, thick and wrinkled fruit, which as a rule is indehiscent. The inflorescence is a raceme, often long, or a spike, sometimes a capitulum. Leaves ternate.--_Ononis_ (Rest-harrow) differs in having monadelphous stamens and in being more shrub-like and bushy, and in having a normal, 2-valved pod, by which characteristic it approaches the Genisteæ. The flowers are generally rose-coloured, solitary, or in few-flowered racemes in the leaf-axils. Thorns (branches) are often present; the leaves are compound with only one small leaflet (the terminal one), or ternate with adnate stipules.

=7.= LOTEÆ. Herbs with ternate or imparipinnate leaves, with entire leaflets. In the latter case, when the lowest pair of leaflets is placed quite close to the sheath, the stalk is wanting, and apparently a trifoliate leaf with large stipules is developed. Flowers in an umbel or capitulum. Stamens monadelphous or diadelphous, the filaments (either all of them, or only the 5 sepal-stamens) are widened at the top.--_Lotus_ (Bird’s-foot-trefoil) has a long, round pod.--_Tetragonolobus._--_Anthyllis_ (Lady’s-finger); the fruit is a nut, which is distributed by the wind by means of the membranous, bladder-like calyx, which completely encloses and falls off with it.

=8.= GENISTEÆ. The majority are shrubs or trees with apparently simple leaves, _i.e._ compound leaves with only one leaflet (the terminal leaflet), or ternate leaves; the stipules in most instances are very small or are entirely wanting; stamens monadelphous.--_Genista_ (Dyer’s-weed) has apparently simple leaves; the branches often terminate in a thorn. ~The strongly-winged stems in _G. sagittalis_ are its most important organs of assimilation. _Bossiæa rufa_ has flat branches, its leaves being reduced to small, pointed stipules.~--_Sarothamnus_ (Broom) has switch-like, angular branches and often both the apparently simple and ternate leaves on the same shoot; style spirally rolled.--_Cytisus_ (Laburnum). _Ulex_ (Furze; ~in _U. europæus_, the seedlings bear a few foliage leaves, but the leaves succeeding these are modified into thorns~); _Spartium_; _Crotalaria_, etc.--_Lupinus_ (Lupin) is allied to this group; it has a thick, often somewhat fleshy pod, and digitate leaves with adnate stipules.--_Retama._

=9.= HEDYSAREÆ are especially recognised by having the ovary divided by transverse septa into as many cells as there are seeds, the fruit thus becomes a _lomentum_, dehiscing transversely into nut-like joints (Fig. 513).--_Ornithopus_ (Bird’s-foot); _Coronilla_; _Hippocrepis_; _Onobrychis_ (Sainfoin) has a fruit with only 1 joint (_i.e._ a 1-seeded nut); _Desmodium_; _Alhagi_; _Hedysarum_, etc.--_Arachis hypogæa_ (Earth-nut) has a pod which is abstricted between the seeds, and is indehiscent, but is not multilocular nor a true lomentum; it is reticulately wrinkled externally, and ripens underground; the basal part of the ovary is prolonged after flowering, attaining a length of several inches, and buries the young fruit in the soil. The embryo is straight.--~_Desmodium gyrans_ is well-known for its motile leaflets.~

=10.= DALBERGIEÆ. 25 genera; especially in Tropical America; the majority are trees, a few shrubs or lianes; the leaves are simple or imparipinnate. The fruit is _indehiscent_ in all; in some it is a winged, in others a wingless _nut_ (_Machærium_, _Dalbergia_, _Centrolobium_, etc.), in others, again, a drupe, _e.g._ in _Dipteryx_ (Tonquin-bean) and _Andira_. In some genera the embryo is straight.

POLLINATION. Especially effected by Bees. The nectar is secreted
by a ring or disc-like portion round the base of the gynœceum or
the inner surface of the receptacle. The flower is constructed
with a peculiar mechanism to ensure cross-pollination by
insects. The pollen is shed just before the flower opens, and
is retained in a pouch formed by the keel. An insect visiting
the flower uses the wings and keel for a landing-stage, and
in attempting to reach the honey presses down the wings and
the keel which are locked together near the standard; the
stylar-brush by this means is forced through the apical opening
of the keel and a little pollen is thus swept out and deposited
upon the abdomen of the visiting insect as it presses against
the apex of the keel; the insect thus carries away pollen and
may effect cross-pollination. In the different flowers this
arrangement is modified in various ways to promote pollination.
5000 species (319 genera); especially in the Tropics, where
many are important forest trees.--The following plants are used
FOR FOOD: _Pisum sativum_ (W. Asia?) and _arvense_ (Italy);
_Phaseolus vulgaris_ (Kidney-bean, American; _Dolichos sinensis_
was known to the Greeks and Romans under the name “φασηλος,”
“phaseolus”), _P. compressus_ (French-bean), etc.; _Faba_
_vulgaris_ (Field-bean, Horse-bean; from the Old World);
_Ervum lens_ (Lentil, Eastern Mediterranean); in tropical
countries the oil-containing seeds of _Arachis hypogæa_.--The
following are FODDER plants: _Vicia sativa_, _Faba vulgaris_,
_Onobrychis sativa_ (Sainfoin), _Medicago sativa_ (Lucerne),
and _lupulina_ (Medick), species of _Trifolium_, _Hedysarum
coronarium_. OFFICINAL: “Liquorice root,” from _Glycyrrhiza
glabra_ (S. Europe); “Red Sandalwood,” from _Pterocarpus
santalinus_ (Tropical E. Asia); Gum Tragacanth, from
_Astragalus_-species (E. Mediterranean); Balsam of Peru, from
_Toluifera pereiræ_, and Balsam of Tolu, from _Toluifera
balsamum_. Calabar-beans, from _Physostigma venenosum_; Kino,
from _Pterocarpus marsupium_; the pith of _Andira araroba_ is
used under the name of “Chrysarobin.”--Of use TECHNICALLY:
_Genista tinctoria_ (yellow dye) and _Indigofera-species_
(Indigo), the bast of _Crotalaria juncea_ (Sunn Hemp); the
seeds of _Dipteryx_, which contain Coumarin, and are highly
scented, and Balsam of _Myroxylon_. POISONOUS: the seeds of
_Laburnum_ (_Cytisus laburnum_), various species of _Lathyrus_,
and _Abrus precatorius_; the latter contain two poisonous
proteids, paraglobulin and albumose, which resemble snake-poison
in their effects. The following are ORNAMENTAL plants:
_Phaseolus multiflorus_ (Scarlet runner, from America), _Robinia
pseudacacia_, _Amorpha_, _Colutea_, _Coronilla_, _Indigofera
dosua_, _Wistaria polystachya_, _Cytisus laburnum_ (Laburnum, S.
Europe, Orient.) and other species.

Order 3. =Mimosaceæ.= The flowers are most frequently hypogynous and _regular_, the æstivation of the corolla is _valvate_ and, in the majority of instances, that of the calyx also. The flower is 4-merous, less frequently 5- or 3-merous.--The flowers are generally small, but are always borne in compact, round _capitula_ or spikes (Fig. 514); they are hypogynous or perigynous. The calyx is generally _gamosepalous_ and the corolla _gamopetalous_, the latter being frequently wanting. The stamens are equal or double the number of the petals (_Mimosa_, etc., in _M. pudica_, _e.g._ S4, P4, A4, G1) or (in _Acacia_, _Inga_, etc.) in a large, indefinite number, free or monadelphous, often united to the corolla (Fig. 514 _b_). The colour of the flower in most cases is due to the long and numerous stamens. The _fruit_ is various. The embryo is _straight_ as in the Cæsalpiniaceæ. _Entada_ and many species of _Mimosa_ have a flat, straight, or somewhat sickle-like pod, which resembles the siliqua of the Cruciferæ in that the sutures (in this instance, however, dorsal and ventral suture) persist as a frame, but the intermediate portion divides, as in the transversely divided siliqua, into as many nut-like portions as there are seeds. Some species have a pod of enormous dimensions. The seeds of _Entada gigalobium_ are often carried from the West Indies to the N. W. coasts of Europe by the Gulf Stream.--The fruit of _Acacia_ in some species is an ordinary pod, in others it is transversely divided, or remains an undivided fruit, a nut.--This order includes both trees and herbaceous plants, which are often thorny; the leaves are usually bipinnate (Fig. 514) and are sensitive, and also possess sleep-movements.--Many Australian Acacias have compound leaves only when young, but when old have _phyllodia_, _i.e._ leaf-like petioles without blades, placed vertically. A large number have thorny stipules, which in some (_Acacia sphærocephala_) attain an enormous size, and serve as a home for ants, which in return protect their host-plant against the attacks of other, leaf-cutting ants.

Other genera besides those mentioned are: _Adenanthera_, _Desmanthus_, _Parkia_, _Inga_ (with rather fleshy, indehiscent fruit), _Calliandra_, etc.

1350 species (30 genera); none natives of Europe, their home
being the Tropics and sub-tropical regions, especially
Australia and Africa.--Fossils in Tertiary.--Gums are found in
many species of _Acacia_, especially the African (Gum arabic)
and Australian, of which some are _officinal_. The bark, and
also the fruits, contain a large amount of _tannic acid_ and
are used as astringents and in tanning (“Bablah” is the fruits
of several species of _Acacia_). Catechu is a valuable tanning
material extracted from the wood of _Acacia catechu_ (E. Ind).
The flowers of _Acacia farnesiana_ (Fig. 514) are used in
the manufacture of perfumes. With us they are cultivated as
ornamental plants, _e.g._ _A. lophantha_ and many others, in
conservatories.

Family 22. =Passiflorinæ.=

The flowers are most frequently regular, 5-merous in the three most external whorls, eucyclic and perigynous or epigynous, less frequently hypogynous. A characteristic feature is that the ovary is _tricarpellary_, _unilocular_, and with 3 _parietal_ placentæ which sometimes meet in the central line (_Cucurbitaceæ_). The styles are generally free and _bifid_. To all these characteristics, however, there are exceptions. ~The Cucurbitaceæ are sometimes placed among the Sympetalæ, close to the Campanulinæ, but they are not allied to the Sympetalæ, from which they differ especially, for instance, in the structure of the ovule. The position of the Begoniaceæ in this family is also open to doubt.~

Order 1. =Passifloraceæ= (=Passion-flowers=). The majority are herbs which climb by means of tendrils (modified branches) and have scattered, stipulate leaves, often palminerved and lobed (Fig. 515). The flowers, which are often large and beautiful, are regular, ☿, with S5, P5, A5, G3; the calyx and corolla are _perigynous_, and immediately inside the corolla is the “corona,” consisting of numerous, tapering, filamentous bodies, or sometimes united in rings, most frequently petaloid and coloured; the stamens are raised on a long, round internode above the _cup-like receptacle_; immediately above these is the gynœceum with its 3 free styles and capitate stigmas; the ovary is unilocular with 3 parietal placentæ. Fruit most frequently a _berry_. The seeds have an aril.

210 species; especially in Tropical America. Several
_Passiflora_-species are ornamental plants, and the fruits of
some species are edible.

Order 2. =Papayaceæ.= The best known representative is the Papaw (_Carica papaya_), a Tropical American tree whose stem is usually unbranched, and bears at its summit several large, palmilobed leaves on long stalks. The stem and leaves have latex. The large, Melon-like berries are edible, and for this reason it is cultivated in the Tropics. Flowers unisexual, with slightly different structure in the ♂-and ♀-flowers, besides intermediate forms. The ♂-flower has a gamopetalous, the ♀-flower a polypetalous corolla.--The milky juice contains a substance with similar action to pepsine. 10 stamens. 5 carpels.

Order 3. =Turneraceæ.= 85 species; especially in America.

Order 4. =Samydaceæ.= 160 species; tropical.

Order 5. =Loasaceæ.= Herbaceous plants seldom shrubs, sometimes climbing, and nearly always studded with _stiff hairs_, in some instances stinging or hooked. The leaves are most frequently palmilobed and without stipules. The flowers are regular, ☿, polypetalous, entirely _epigynous_, with 4–5 sepals, petals and stamens, or more frequently (by splitting) many stamens, those which are placed before the sepals being generally barren and more or less petaloid; carpels most frequently 3, united into an inferior, unilocular ovary with 3 parietal placentæ, above which the receptacle is generally more or less prolonged. Fruit a capsule; in _Gronovia_ an ovary with 1 ovule and fruit a nut.

115 species; principally from S. Am. A number of annuals are
often grown in our gardens: _Bartonia aurea_ (California);
_Mentzelia_; _Cajophora_; _Gronovia_.

Order 6. =Datiscaceæ.= 4 species, especially in the Tropics.--_Datisca cannabina_ (Asia Minor) resembles the Hemp in external appearance. The flowers are diœcious, insignificant; ♂-flowers: a low, gamosepalous calyx, no corolla, and an indefinite number of stamens; ♀-flowers; _epigynous_; ovary unilocular with free, mostly bifid, styles, and generally 3 parietal placentæ. In most cases the ovary is not entirely closed at the top (as in _Reseda_).

Order 7. =Begoniaceæ.= This order principally comprises herbs or under-shrubs with succulent stems (having scattered vascular bundles in the pith); the leaves are arranged in two rows (a divergence of 1/2) and _are asymmetrical_, as a rule more or less obliquely cordate, or ovate with cordate base (Fig. 516); large, caducous stipules are present. Inflorescences dichasial, or unipared scorpioid cymes; the flowers are unisexual; the first ones (the oldest) are ♂-flowers, while ♀-flowers are found especially on the younger axes. The ♂-flowers have most frequently 2 + 2 coloured perianth-leaves, and many stamens collected into a head in the centre of the flower; the ♀-flowers are _epigynous_ with 5 coloured perianth-leaves (placed spirally with a divergence of 2/5) and a trilocular ovary, bearing 3 bifid styles and 3 wings (the wings usually of unequal size); in the inner angle of each loculus there is one large projecting placenta, or two plate-like placentæ (the bent back edges of the carpels) studded with ovules. Fruit a capsule, with many extremely small seeds.--_Begonia._

420 species; almost all from the Tropics (Am., Asia).--Many
species, with varieties and hybrids, are ornamental plants in
houses and conservatories, chiefly on account of the form,
colour and markings of their leaves; but also for their very
beautiful flowers. They reproduce easily by adventitious buds
from leaves and portions of leaves placed on damp soil; some
have bulbils. Like the Oxalideæ they contain an acid sap.