Chapter IX: Part 9

The products of the break-rolls are treated by what are known as
scalpers, which are simply machines for sorting out these products for
further treatment. Scalpers may either be revolving reels or flat
sieves. The sieve is the favourite form of scalper on account of its
gentle action. Scalping requires a separating and sifting, not a
scouring action. The break products are usually separated on a sieve
covered with wire or perforated zinc plates. Generally speaking, two
sieves are in one frame and are run at a slight incline. The throughs
of the top sieve fall on the sieve below, while the rejections or
overtails of the first sieve are fed to the next break. The
"throughs," or what has passed this sieve, are graded by the next
sieve, the tailings going to a purifier, while the throughs may be
freed from what flour adheres to them by a centrifugal dressing
machine and then treated by another purifier. A form of scalper which
has come into general use on the continent of Europe, and to a lesser
extent in Great Britain and America, is known as the plansifter. This
machine, of Hungarian origin, is simply a collection of superimposed
flat sieves in one box, and will scalp or sort out any kind of break
stock very efficiently. A system of grading the tailings, that is, the
rejections of the scalpers, introduced by James Harrison Carter
(Carter-Zimmer patent), was known as pneumatic sorting. Its object was
to supplement the work of the scalpers by classifying the tailings by
means of air-currents. To this end each scalper was followed by a
machine arranged somewhat like a gravity purifier; that is to say, a
current of air drawn through the casing of the sorter allowed the
heaviest and best material to drop down straight, while the lighter
stuff was deposited in one or other of further compartments formed by
obliquely placed adjustable cant boards. So searching was this
grading, that from the first sorter of a four-break plant four
separations would be obtained, the first going to the second break,
the second joining the first separation from the second sorter and
being fed to the third break, while the third went with the best
separation of the third sorter to the fourth break, and the last
separation from all the sorters went straight into the bran sack. The
work of the break-rolls was greatly simplified and reduced by this
sorting process, as each particle of broken wheat went exactly to that
pair of break-rollers for which it was suitable, instead of all the
material being run indiscriminately through all the break-rollers and
thereby being cut up with the necessary result of increasing the
production of small bran.

Purifiers.

The object of the purifier, a machine on which milling engineers have
lavished much thought and labour, is to get away from the semolina and
middlings as much impure matter as possible, that those products may
be pure, as millers say, for reduction to flour by the smooth rolls.
The purifiers used in British mills take advantage of the fact that
the more valuable portions of the wheat berry are heavier than the
less valuable particles, such as bran and fibrous bodies, and a
current of air is employed to weigh these fragments of the wheat berry
as in a balance and to separate them while they pass over a
silk-covered sieve. To this end the semolina or middlings are fed on a
sieve vibrated by an eccentric and set at a slight downward angle.
This sieve is installed in an air-tight longitudinal wooden chamber
with glass windows on either side, through which the process of
purifying can be watched. Upwards through this sieve a fan constantly
draws a current of air, which, raising the stock upwards, allows the
heavier and better material to remain below while the lighter
particles are lifted off and fall on side platforms or channels,
whence they are carried forward and delivered separately. The good
material drops through the meshes of the silk, and is collected by a
worm. It is usual to clothe the sieve in sections with several
different meshes of silk so that stock of almost identical value, but
differing size, may be treated with uniform accuracy. In good
purifiers the strength of the current can be regulated at will in each
section. The tailings of a purifier do not usually exceed 10 to 15% of
the feed. The clothing of purifier sheets must be nicely graduated to
the clothing of the preceding machines. Repurification and even
tertiary purification may be necessary under certain conditions. In
Hungary and other parts of Europe, gravity purifiers are much in use.
Here the material is guided along an open sieve set at a slight angle,
while an air-current is drawn up at an acute angle. Under the sieve
may be arranged a series of inclined boards, the position of which can
be varied as required. The heaviest and most valuable products resist
the current and drop straight down, while lighter material is carried
off to further divisions.

Smooth rolls.

From the purifier all the stock except the tailings, which may require
other treatment, should go to the smooth rollers to be made into
flour, but here the rollerman will have to exercise great care and
discretion. Many of the remarks already made in regard to break-rolls
apply to smooth rolls, notably in respect of parallelism. But instead
of a cutting action, the smooth rolls press the material fed to them
into flour. This pressure, however, must be applied with great
discrimination, large semolina with impurities attached requiring
quite different treatment from that called for by small pure
middlings. The pressure on the stock must be just sufficient and no
more. Reduction rolls are usually run at a differential speed of about
2 to 3. The feed must be carefully graded, because to pass stock of
varying size through a pair of smooth rolls would be fatal to good
work. Scratch rolls very finely grooved are used for cracking impure
semolina or for reducing the tailings of purifiers. The latter often
hold fragments of bran, which are best detached by rolls grooved about
36 to the inch and run at a differential of 3 to 1. The reduction
requires even more roll surface than the break system. To do
first-class work a mill should have at least 35 to 40 in. on the
breaks and 50 in. on the reduction for each sack of 280 lb. of flour
per hour. Many engineers consider 100 to 110 in. on the break, scratch
and smooth rolls not too much.

Dressing.

The dressing out of the flour from the stock reduced on smooth rolls
is generally effected by centrifugal machines, which consist of a
slowly revolving cylinder provided with an internal shaft on which are
keyed a number of iron beaters that run at a speed of about 200
revolutions a minute, and fling the feed against the silk clothing of
the cylinder. What goes through the silk is collected by a worm
conveyor at the bottom of the machine. Most centrifugals have
so-called "cut-off" sheets, with internal divisions in the tail end;
these are intended to separate some intermediate products, which,
having been freed from floury particles, are treated on some other
machine, such as a pair of rolls either direct or after a purifier.
The centrifugal is undoubtedly an efficient flour separator, but the
plansifters already mentioned are also good flour-dressers, especially
in dry climates. A plansifter mill will have no centrifugals, except
one or two at the tail end where the material gets more sticky and
requires more severe treatment.

The yield of flour obtained in a British roller mill averages 70 to
73% of the wheat berry. The residue, with the exception of a very
small proportion of waste, is offal, which is divided into various
grades and sold. Profitable markets for British-made bran have been
found in Scandinavia, and especially in Denmark. In millstone milling
the yield of flour probably averaged 75 to 80%, but a certain
proportion of this was little more than offal. The length of the flour
yield taken by British millers varies in different parts of the
kingdom, because demand varies. In one locality high-class patents may
be at a premium; in another the call is for a straight grade, i.e. a
flour containing as much of the farinaceous substance as can be won
from the wheat berry. In one district there is a sale for rich offals,
that is, offals with plenty of flour adhering; in another there may be
no demand for such offals. Hence, though the general principles of
roller milling as given above hold good all over the country, yet in
practice the work of each mill is varied more or less to suit the
peculiarities of the local trade.

Bleaching of flour.

Early in the 19th century a French chemist, J.J.E. Poutet, discovered
that nitrous acid and oxides of nitrogen act on some fluid and
semi-fluid vegetable oils, removing their yellow tinge and converting
a considerable portion of their substance into a white solid. The
importance of this discovery, when the physical constitution of wheat
is considered, is obvious, but it was years before any attempt was
made to bleach flour. The first attempts at bleaching seem to have
been made on the wheat itself rather than on the flour. In 1879 a
process was patented for bleaching grain by means of chlorine gas, and
about 1891 a suggestion was made for bleaching grain by means of
electrolysed sea-water. In 1895 a scheme was put forward for treating
grain with sulphurous acid, and about two years later it was proposed
to subject both grain and flour to the influence of electric currents.
In 1893 a patent was granted for the purification of flour by means of
fresh air or oxygen, and three years later another inventor proposed
to employ the Rontgen rays for the same purpose. In 1898 Emile Frichot
took out a patent for using ozone and ozonized air for
flour-bleaching. The patent (No. 1661 of 1901) taken out by J. & S.
Andrews of Belfast recited that flour is known to improve greatly if
kept for some time after grinding, and the purpose of the invention it
covered was to bring about this improvement or conditioning not only
immediately after grinding, but also to a greater extent than can be
effected by keeping. The process consisted in subjecting the flour to
the action of a suitable gaseous oxidizing medium; the inventors
preferred air carrying a minute quantity of nitric acid or peroxide of
nitrogen, but they did not confine themselves to those compounds,
having found that chlorine, bromine and other substances capable of
liberating oxygen were also more or less efficacious. They claimed
that while exercising no deleterious action their treatment made the
flour whiter, improved its baking qualities, and rendered it less
liable to be attacked by mites or other organisms. Under the patent,
No. 14006 of 1903, granted to J.N. Alsop of Kentucky the flour was
treated with atmospheric air which had been subjected to the action of
an arc or flaming discharge of electricity, with the purpose of
purifying it and improving its nutritious properties. The Andrews and
Alsop patents became the objects of extended litigation in the English
courts, and it was held that the gaseous medium employed by Alsop was
substantially the same as that employed by Andrews, though produced
electrically instead of chemically, and therefore that the Alsop
process was an infringement of the Andrews patent. Various other
patents for more or less similar processes have also been taken out.
(G. F. Z.)

FLOURENS, GUSTAVE (1838-1871), French revolutionist and writer, a son of J.P. Flourens (1794-1867), the physiologist, was born at Paris on the 4th of August 1838. In 1863 he undertook for his father a course of lectures at the College de France, the subject of which was the history of mankind. His theories as to the manifold origin of the human race, however, gave offence to the clergy, and he was precluded from delivering a second course. He then went to Brussels, where he published his lectures under the title of _Histoire de l'homme_ (1863); he next visited Constantinople and Athens, took part in the Cretan insurrection of 1866, spent some time in Italy, where an article of his in the _Popolo d'Italia_ caused his arrest and imprisonment, and finally, having returned to France, nearly lost his life in a duel with Paul de Cassagnac, editor of the _Pays_. In Paris he devoted his pen to the cause of republicanism, and at length, having failed in an attempt to organize a revolution at Belleville on the 7th of February 1870, found himself compelled to flee from France. Returning to Paris on the downfall of Napoleon, he soon placed himself at the head of a body of 500 tirailleurs. On account of his insurrectionary proceedings he was taken prisoner at Creteil, near Vincennes, by the provisional government, and confined at Mazas on the 7th of December 1870, but was released by his men on the night of January 21-22. On the 18th of March he joined the Communists. He was elected a member of the commune by the 20th arrondissement, and was named colonel. He was one of the most active leaders of the insurrection, and in a sortie against the Versailles troops in the morning of the 3rd of April was killed in a hand-to-hand conflict at Rueil, near Malmaison. Besides his _Science de l'homme_ (Paris, 1869), Gustave Flourens was the author of numerous fugitive pamphlets.

See C. Proles, _Les Hommes de la revolution de 1871_ (Paris, 1898).

FLOURENS, MARIE JEAN PIERRE (1794-1867), French physiologist, was born at Maureilhan, near Beziers, in the department of Herault, on the 15th of April 1794. At the age of fifteen he began the study of medicine at Montpellier, where in 1823 he received the degree of doctor. In the following year he repaired to Paris, provided with an introduction from A.P. de Candolle, the botanist, to Baron Cuvier, who received him kindly, and interested himself in his welfare. At Paris Flourens engaged in physiological research, occasionally contributing to literary publications; and in 1821, at the Athenee there, he gave a course of lectures on the physiological theory of the sensations, which attracted much attention amongst men of science. His paper entitled _Recherches experimentales sur les proprietes et les fonctions du systeme nerveux dans les animaux vertebres_, in which he, from experimental evidence, sought to assign their special functions to the cerebrum, corpora quadrigemina and cerebellum, was the subject of a highly commendatory report by Cuvier, adopted by the French Academy of Sciences in 1822. He was chosen by Cuvier in 1828 to deliver for him a course of lectures on natural history at the College de France, and in the same year became, in succession to L.A.G. Bosc, a member of the Institute, in the division "Economie rurale." In 1830 he became Cuvier's substitute as lecturer on human anatomy at the Jardin du Roi, and in 1832 was elected to the post of titular professor, which he vacated for the professorship of comparative anatomy created for him at the museum of the Jardin the same year. In 1833 Flourens, in accordance with the dying request of Cuvier, was appointed a perpetual secretary of the Academy of Sciences; and in 1838 he was returned as a deputy for the arrondissement of Beziers. In 1840 he was elected, in preference to Victor Hugo, to succeed J.F. Michaud at the French Academy; and in 1845 he was created a commander of the legion of honour, and in the next year a peer of France. In March 1847 Flourens directed the attention of the Academy of Sciences to the anaesthetic effect of chloroform on animals. On the revolution of 1848 he withdrew completely from political life; and in 1855 he accepted the professorship of natural history at the College de France. He died at Montgeron, near Paris, on the 6th of December 1867.

Besides numerous shorter scientific memoirs, Flourens
published--_Essai sur quelques points de la doctrine de la revulsion
et de la derivation_ (Montpellier, 1813); _Experiences sur le systeme
nerveux_ (Paris, 1825); _Cours sur la generation, l'ovologie, et
l'embryologie_ (1836); _Analyse raisonnee des travaux de G. Cuvier_
(1841); _Recherches sur le developpement des os et des dents_ (1842);
_Anatomie generale de la peau et des membranes muqueuses_ (1843);
_Buffon, histoire de ses travaux et de ses idees_ (1844); _Fontenelle,
ou de la philosophie moderne relativement aux sciences physiques_
(1847); _Theorie experimentale de la formation des os_ (1847);
_Oeuvres completes de Buffon_ (1853); _De la longevite humaine et de
la quantite de vie sur le globe_ (1854), numerous editions; _Histoire
de la decouverte de la circulation du sang_ (1854); _Cours de
physiologie comparee_ (1856); _Recueil des eloges historiques_ (1856);
_De la vie et de l'intelligence_ (1858); _De la raison, du genie, et
de la folie_ (1861); _Ontologie naturelle_ (1861); _Examen du livre de
M. Darwin sur l'Origine des Especes_ (1864). For a list of his papers
see the Royal Society's _Catalogue of Scientific Papers_.

FLOWER, SIR WILLIAM HENRY (1831-1899), English biologist, was born at Stratford-on-Avon on the 30th of November 1831. Choosing medicine as his profession, he began his studies at University College, London, where he showed special aptitude for physiology and comparative anatomy and took his M.B. degree in 1851. He then joined the Army Medical Service, and went out to the Crimea as assistant-surgeon, receiving the medal with four clasps. On his return to England he became a member of the surgical staff of the Middlesex hospital, London, and in 1861 succeeded J.T. Quekett as curator of the Hunterian Museum of the Royal College of Surgeons of England. In 1870 he also became Hunterian professor, and in 1884, on the death of Sir Richard Owen, was appointed to the directorship of the Natural History Museum at South Kensington. He died in London on the 1st of July 1899. He made valuable contributions to structural anthropology, publishing, for example, complete and accurate measurements of no less than 1300 human skulls, and as a comparative anatomist he ranked high, devoting himself especially to the study of the mammalia. He was also a leading authority on the arrangement of museums. The greater part of his life was spent in their administration, and in consequence he held very decided views as to the principles upon which their specimens should be set out. He insisted on the importance of distinguishing between collections intended for the use of specialists and those designed for the instruction of the general public, pointing out that it was as futile to present to the former a number of merely typical forms as to provide the latter with a long series of specimens differing only in the most minute details. His ideas, which were largely and successfully applied to the museums of which he had charge, gained wide approval, and their influence entitles him to be looked upon as a reformer who did much to improve the methods of museum arrangement and management. In addition to numerous original papers, he was the author of _An Introduction to the Osteology of the Mammalia_ (1870); _Fashion in Deformity_ (1881); _The Horse: a Study in Natural History_ (1890); _Introduction to the Study of Mammals, Living and Extinct_ (1891); _Essays on Museums and other Subjects_ (1898). He also wrote many articles for the ninth edition of the _Encyclopaedia Britannica_.

FLOWER (Lat. _flos_, _floris_; Fr. _fleur_), a term popularly used for the bloom or blossom of a plant, and so by analogy for the fairest, choicest or finest part or aspect of anything, and in various technical senses. Here we shall deal only with its botanical interest. It is impossible to give a rigid botanical definition of the term "flower." The flower is a characteristic feature of the highest group of the plant kingdom--the flowering plants (Phanerogams)--and is the name given to the association of organs, more or less leaf-like in form, which are concerned with the production of the fruit or seed. In modern botanical works the group is often known as the seed-plants (Spermatophyta). As the seed develops from the ovule which has been fertilized by the pollen, the essential structures for seed-production are two, viz. the pollen-bearer or _stamen_ and the ovule-bearer or _carpel_. These are with few exceptions foliar structures, known in comparative morphology as sporophylls, because they bear the spores, namely, the microspores or pollen-grains which are developed in the microsporangia or pollen-sacs, and the megaspore, which is contained in the ovule or megasporangium.

In Gymnosperms (q.v.), which represent the more primitive type of seed-plants, the micro- or macro-sporophylls are generally associated, often in large numbers, in separate cones, to which the term "flower" has been applied. But there is considerable difference of opinion as to the relation between these cones and the more definite and elaborate structure known as the flower in the higher group of seed-plants--the Angiosperms (q.v.)--and it is to this more definite structure that we generally refer in using the term "flower."

s, Sepals transformed into leaves.

p, Petals multiplied at the expense of the stamens, which are reduced
in number.

c, Coloured leaves representing abortive carpels.

a, Axis prolonged, bearing an imperfect flower at its apex.]

Flowers are produced from flower-buds, just as leaf-shoots arise from leaf-buds. These two kinds of buds have a resemblance to each other as regards the arrangement and the development of their parts; and it sometimes happens, from injury and other causes, that the part of the axis which, in ordinary cases, would produce a leaf-bud, gives origin to a flower-bud. A flower-bud has not in ordinary circumstances any power of extension by the continuous development of its apex. In this respect it differs from a leaf-bud. In some cases, however, of monstrosity, especially seen in the rose (fig. 1), the central part is prolonged, and bears leaves or flowers. In such cases the flowers, so far as their functional capabilities are concerned, are usually abortive. This phenomenon is known as proliferation of the floral axis.

Flower-buds, like leaf-buds, are produced in the axil of leaves, which are called _bracts_.

Bracts.

The term _bract_ is properly applied to the leaf from which the primary floral axis, whether simple or branched, arises, while the leaves which arise on the axis between the bract and the outer envelope of the flower are _bracteoles_ or _bractlets_. Bracts sometimes do not differ from the ordinary leaves, as in _Veronica hederifolia_, _Vinca_, _Anagallis_ and _Ajuga_. In general as regards their form and appearance they differ from ordinary leaves, the difference being greater in the upper than in the lower branches of an inflorescence. They are distinguished by their position at the base of the flower or flower-stalk. Their arrangement is similar to that of the leaves. When the flower is sessile the bracts are often applied closely to the calyx, and may thus be confounded with it, as in the order Malvaceae and species of _Dianthus_ and winter aconite (_Eranthis_), where they have received the name of _epicalyx_ or _calyculus_. In some Rosaceous plants an epicalyx is present, due to the formation of stipulary structures by the sepals. In many cases bracts act as protective organs, within or beneath which the young flowers are concealed in their earliest stage of growth.

When bracts become coloured, as in _Amherstia nobilis_, _Euphorbia splendens_, _Erica elegans_ and _Salvia splendens_, they may be mistaken for parts of the corolla. They are sometimes mere scales or threads, and at other times are undeveloped, giving rise to the _ebracteate_ inflorescence of Cruciferae and some Boraginaceae. Sometimes they are empty, no flower-buds being produced in their axil. A series of empty coloured bracts terminates the inflorescence of _Salvia Horminum_. The smaller bracts or bracteoles, which occur among the subdivisions of a branching inflorescence, often produce no flower-buds, and thus anomalies occur in the floral arrangements. Bracts are occasionally persistent, remaining long attached to the base of the peduncles, but more usually they are deciduous, falling off early by an articulation. In some instances they form part of the fruit, becoming incorporated with other organs. Thus, the cones of firs and the stroboli of the hop are composed of a series of spirally arranged bracts covering fertile flowers; and the scales on the fruit of the pine-apple are of the same nature. At the base of the general umbel in umbelliferous plants a whorl of bracts often exists, called a _general involucre_, and at the base of the smaller umbels or umbellules there is a similar leafy whorl called an _involucel_ or _partial involucre_. In some instances, as in fool's-parsley, there is no general involucre, but simply an involucel; while in other cases, as in fennel or dill (fig. 15), neither involucre nor involucel is developed. In Compositae the name involucre is applied to the bracts surrounding the head of flowers (fig. 2, i), as in marigold, dandelion, daisy, artichoke. This involucre is frequently composed of several rows of leaflets, which are either of the same or of different forms and lengths, and often lie over each other in an imbricated manner. The leaves of the involucre are spiny in thistles and in teazel (_Dipsacus_), and hooked in burdock. Such whorled or verticillate bracts generally remain separate (_polyphyllous_), but may be united by cohesion (_gamophyllous_), as in many species of _Bupleurum_ and in _Lavatera_. In Compositae besides the involucre there are frequently chaffy and setose bracts at the base of each flower, and in Dipsacaceae a membranous tube surrounds each flower. These structures are of the nature of an epicalyx. In the acorn the _cupule_ or cup (fig. 3) is formed by a growing upwards of the flower-stalk immediately beneath the flower, upon which scaly or spiny protuberances appear; it is of the nature of bracts. Bracts also compose the husky covering of the hazel-nut.

FIG. 3.--Cupule of _Quercus Aegilops_. cp, Cupule; gl, fruit. (After Duchartre.)]

When bracts become united, and overlie each other in several rows, it often happens that the outer ones do not produce flowers, that is, are empty or sterile. In the artichoke the outer imbricated scales or bracts are in this condition, and it is from the membranous white scales or bracts (_paleae_) forming the choke attached to the edible receptacle that the flowers are produced. The sterile bracts of the daisy occasionally produce capitula, and give rise to the hen-and-chickens daisy. In place of developing flower-buds, bracts may, in certain circumstances, as in proliferous or viviparous plants, produce leaf-buds.

A sheathing bract enclosing one or several flowers is called a _spathe_. It is common among Monocotyledons, as _Narcissus_ (fig. 4), snow-flake, _Arum_ and palms. In some palms it is 20 ft. long, and encloses 200,000 flowers. It is often associated with that form of inflorescence termed the _spadix_, and may be coloured, as in _Anthurium_, or white, as in arum lily (_Richardia aethiopica_). When the spadix is compound or branching, as in palms, there are smaller spathes, surrounding separate parts of the inflorescence. The spathe protects the flowers in their young state, and often falls off after they are developed, or hangs down in a withered form, as in some palms, _Typha_ and _Pothos_. In grasses the outer scales or glumes of the spikelets are sterile bracts (fig. 5, gl); and in Cyperaceae bracts enclose the organs of reproduction. Bracts are frequently changed into complete leaves. This change is called _phyllody_ of bracts, and is seen in species of _Plantago_, especially in the variety of _Plantago media_, called the rose-plantain in gardens, where the bracts become leafy and form a rosette round the flowering axis. Similar changes occur in _Plantago major_, _P. lanceolata_, _Ajuga reptans_, dandelion, daisy, dahlia and in umbelliferous plants. The conversion of bracts into stamens (_staminody_ of bracts) has been observed in the case of _Abies excelsa_. A lengthening of the axis of the female strobilus of Coniferae is not of infrequent occurrence in _Cryptomeria japonica_, larch (_Larix europaea_), &c., and this is usually associated with a leaf-like condition of the bracts, and sometimes even with the development of leaf-bearing shoots in place of the scales.

The arrangement of the flowers on the axis, or the ramification of the floral axis, is called the _inflorescence_. The primary axis of the inflorescence is sometimes called the _rachis_; its branches, whether terminal or lateral, which form the stalks supporting flowers or clusters of flowers, are _peduncles_, and if small branches are given off by it, they are called _pedicels_. A flower having a stalk is called _pedunculate_ or _pedicellate_; one having no stalk is _sessile_. In describing a branching inflorescence, it is common to speak of the rachis as the _primary_ floral axis, its branches as the _secondary_ floral axes, their divisions as the _tertiary_ floral axes, and so on; thus avoiding any confusion that might arise from the use of the terms _rachis_, _peduncle_ and _pedicel_.

The _peduncle_ is simple, bearing a single flower, as in primrose; or branched, as in London-pride. It is sometimes succulent, as in the cashew, in which it forms the large coloured expansion supporting the nut; spiral, as in _Cyclamen_ and _Vallisneria_; or spiny, as in _Alyssum spinosum_. When the peduncle proceeds from radical leaves, that is, from an axis which is so shortened as to bring the leaves close together in the form of a cluster, as in the primrose, auricula or hyacinth, it is termed a _scape_. The floral axis may be shortened, assuming a flattened, convex or concave form, and bearing numerous flowers, as in the artichoke, daisy and fig (fig. 6). The floral axis sometimes appears as if formed by several peduncles united together, constituting a fasciated axis, as in the cockscomb, in which the flowers form a peculiar crest at the apex of the flattened peduncles. Adhesions occasionally take place between the peduncle and the bracts or leaves of the plant, as in the lime-tree (fig. 7). The adhesion of the peduncles to the stem accounts for the extra-axillary position of flowers, as in many Solanaceae. When this union extends for a considerable length along the stem, several leaves may be interposed between the part where the peduncle becomes free and the leaf whence it originated, and it may be difficult to trace the connexion. The peduncle occasionally becomes abortive, and in place of bearing a flower, is transformed into a tendril; at other times it is hollowed at the apex, so as apparently to form the lower part of the outer whorl of floral leaves as in _Eschscholtzia_. The termination of the peduncle, or the part on which the whorls of the flower are arranged, is called the _thalamus_, _torus_ or _receptacle_.

FIG. 7.--Inflorescence of the Lime (_Tilia platyphyllos_) (nat. size).

a, Branch.

b, Petiole with axillary bud. Attached to the peduncle is the bract
(h).

k, Calyx.

c, Corolla.

s, Stamens.

f, Ovary.

kn, Flower-bud.]

FIG. 8.--Raceme of _Linaria striata_. d, bract.]

Inflorescence.

There are two distinct types of inflorescence--one in which the flowers arise as lateral shoots from a primary axis, which goes on elongating, and the lateral shoots never exceed in their development the length of the primary axis beyond their point of origin. The flowers are thus always _axillary_. Exceptions, such as in cruciferous plants, are due to the non-appearance of the bracts. In the other type the primary axis terminates in a single flower, but lateral axes are given off from the axils of the bracts, which again repeat the primary axis; the development of each lateral axis is stronger than that of the primary axis beyond its point of origin. The flowers produced in this inflorescence are thus _terminal_. The first kind of inflorescence is _indeterminate_, _indefinite_ or _axillary_. Here the axis is either elongated, producing flower-buds as it grows, the lower expanding first (fig. 8), or it is shortened and depressed, and the outer flowers expand first (fig. 9). The expansion of the flowers is thus _centripetal_, that is, from base to apex, or from circumference to centre.

The second kind of inflorescence is _determinate_, _definite_ or _terminal_. In this the axis is either elongated and ends in a solitary flower, which thus terminates the axis, and if other flowers are produced, they belong to secondary axes farther from the centre; or the axis is shortened and flattened, producing a number of separate floral axes, the central one expanding first, while the others are developed in succession farther from the centre. The expansion of the flowers is in this case _centrifugal_, that is, from apex to base, or from centre to circumference. It is illustrated in fig. 10, _Ranunculus bulbosus_; a' is the primary axis swollen at the base in a bulb-like manner b, and with roots proceeding from it. From the leaves which are radical proceeds the axis ending in a solitary terminal flower f'. About the middle of this axis there is a leaf or bract, from which a secondary floral axis a" is produced, ending in a single flower f", less advanced than the flower f'. This secondary axis bears a leaf also, from which a tertiary floral axis a"' is produced, bearing an unexpanded solitary flower f"'. From this tertiary axis a fourth is in progress of formation. Here f' is the termination of the primary axis, and this flower expands first, while the other flowers are developed centrifugally on separate axes.

A third series of inflorescences, termed _mixed_, may be recognized. In them the primary axis has an arrangement belonging to the opposite type from that of the branches, or vice versa. According to the mode and degree of development of the lateral shoots and also of the bracts, various forms of both inflorescences result.

Amongst indefinite forms the simplest occurs when a lateral shoot produced in the axil of a large single foliage leaf of the plant ends in a single flower, the axis of the plant elongating beyond, as in _Veronica hederifolia_, _Vinca minor_ and _Lysimachia nemorum_. The flower in this case is _solitary_, and the ordinary leaves become bracts by producing flower-buds in place of leaf-buds; their number, like that of the leaves of this main axis, is indefinite, varying with the vigour of the plant. Usually, however, the floral axis, arising from a more or less altered leaf or bract, instead of ending in a solitary flower, is prolonged, and bears numerous bracteoles, from which smaller peduncles are produced, and those again in their turn may be branched in a similar way. Thus the flowers are arranged in groups, and frequently very complicated forms of inflorescence result. When the primary peduncle or floral axis, as in fig. 8, is elongated, and gives off pedicels, ending in single flowers, a _raceme_ is produced, as in currant, hyacinth and barberry. If the secondary floral axes give rise to tertiary ones, the raceme is branching, and forms a _panicle_, as in _Yucca gloriosa_. If in a raceme the lower flower-stalks are developed more strongly than the upper, and thus all the flowers are nearly on a level, a _corymb_ is formed, which may be simple, as in fig. 11, where the primary axis a' gives off secondary axes a", a", which end in single flowers; or branching, where the secondary axes again subdivide. If the pedicels are very short or wanting, so that the flowers are sessile, a _spike_ is produced, as in _Plantago_ and vervain (_Verbena officinalis_) (fig. 12). If the spike bears unisexual flowers, as in willow or hazel (fig. 13), it is an _amentum_ or _catkin_, hence such trees are called _amentiferous_; at other times it becomes succulent, bearing numerous flowers, surrounded by a sheathing bract or spathe, and then it constitutes a _spadix_, which may be simple, as in _Arum maculatum_ (fig. 14), or branching as in palms. A spike bearing female flowers only, and covered with scales, is a _strobilus_, as in the hop. In grasses there are usually numerous sessile flowers arranged in small spikes, called _locustae_ or _spikelets_, which are either set closely along a central axis, or produced on secondary axes formed by the branching of the central one; to the latter form the term panicle is applied.

FIG. 11.--Corymb of _Cerasus Mahaleb_, terminating an abortive branch, at the base of which are modified leaves in the form of scales, e. a', Primary axis; a", secondary axes bearing flowers; b, bract in the axils of which the secondary axes arise.

FIG. 12.--Spike of Vervain (_Verbena officinalis_), showing sessile flowers on a common rachis. The flowers at the lower part of the spike have passed into fruit, those towards the middle are in full bloom, and those at the top are only in bud.

FIG. 13.--Amentum or catkin of Hazel (_Corylus Avellana_), consisting of an axis or rachis covered with bracts in the form of scales, each of which covers a male flower, the stamens of which are seen projecting beyond the scale. The catkin falls off in a mass, separating from the branch by an articulation.]

FIG. 14.--Spadix of _Arum maculatum_. (After Wossidlo.) a, Female flowers; b, male flowers; c, hairs representing sterile flowers.]

If the primary axis, in place of being elongated, is contracted, it gives rise to other forms of indefinite inflorescence. When the axis is so shortened that the secondary axes arise from a common point, and spread out as _radii_ of nearly equal length, each ending in a single flower or dividing again in a similar radiating manner, an _umbel_ is produced, as in fig. 15. From the primary floral axis a the secondary axes come off in a radiating or umbrella-like manner, and end in small umbels b, which are called _partial umbels_ or _umbellules_. This inflorescence is seen in hemlock and other allied plants, which are hence called umbelliferous. If there are numerous flowers on a flattened, convex or slightly concave receptacle, having either very short pedicels or none, a _capitulum_ (head) is formed, as in dandelion, daisy and other composite plants (fig. 2), also in scabious (fig. 9) and teazel. In the American button-bush the heads are globular, in some species of teazel elliptical, while in scabious and in composite plants, as sunflower, dandelion, thistle, centaury and marigold, they are somewhat hemispherical, with a flattened, slightly hollowed, or convex disk. If the margins of such a receptacle be developed upwards, the centre not developing, a concave receptacle is formed, which may partially or completely enclose a number of flowers that are generally unisexual. This gives rise to the peculiar inflorescence of _Dorstenia_, or to that of the fig (fig. 6), where the flowers are placed on the inner surface of the hollow receptacle, and are provided with bracteoles. This inflorescence has been called a _hypanthodium_.

Lastly, we have what are called _compound indefinite_ inflorescences. In these forms the lateral shoots, developed centripetally upon the primary axis, bear numerous bracteoles, from which floral shoots arise which may have a centripetal arrangement similar to that on the mother shoot, or it may be different. Thus we may have a group of racemes, arranged in a racemose manner on a common axis, forming a raceme of racemes or compound raceme, as in _Astilbe_. In the same way we may have compound umbels, as in hemlock and most Umbelliferae (fig. 15), a compound spike, as in rye-grass, a compound spadix, as in some palms, and a compound capitulum, as in the hen-and-chickens daisy. Again, there may be a raceme of capitula, that is, a group of capitula disposed in a racemose manner, as in _Petasites_, a raceme of umbels, as in ivy, and so on, all the forms of inflorescence being indefinite in disposition. In _Eryngium_ the shortening of the pedicels changes an umbel into a capitulum.

The simplest form of the definite type of the inflorescence is seen in _Anemone nemorosa_ and in gentianella (_Gentiana acaulis_), where the axis terminates in a single flower, no other flowers being produced upon the plant. This is a _solitary terminal_ inflorescence. If other flowers were produced, they would arise as lateral shoots from the bracts below the first-formed flower. The general name of _cyme_ is applied to the arrangement of a group of flowers in a definite inflorescence. A _cymose_ inflorescence is an inflorescence where the primary floral axis before terminating in a flower gives off one or more lateral unifloral axes which repeat the process--the development being only limited by the vigour of the plant. The floral axes are thus centrifugally developed. The cyme, according to its development, has been characterized as _biparous_ or _uniparous_. In fig. 16 the biparous cyme is represented in the flowering branch of _Cerastium_. Here the primary axis t ends in a flower, which has passed into the state of fruit. At its base two leaves are produced, in each of which arise secondary axes t' t', ending in single flowers, and at the base of these axes a pair of opposite leaves is produced, giving rise to tertiary axes t" t", ending in single flowers, and so on. The term _dichasium_ has also been applied to this form of cyme.

In the natural order Carophyllaceae (pink family) the dichasial form of inflorescence is very general. In some members of the order, as _Dianthus barbatus_, _D. carthusianorum_, &c., in which the peduncles are short, and the flowers closely approximated, with a centrifugal expansion, the inflorescence has the form of a contracted dichasium, and receives the name of _fascicle_. When the axes become very much shortened, the arrangement is more complicated in appearance, and the nature of the inflorescence can only be recognized by the order of opening of the flowers. In Labiate plants, as the dead-nettle (_Lamium_), the flowers are produced in the axil of each of the foliage leaves of the plant, and they appear as if arranged in a simple whorl of flowers. But on examination it is found that there is a central flower expanding first, and from its axis two secondary axes spring bearing solitary flowers; the expansion is thus centrifugal. The inflorescence is therefore a contracted dichasium, the flowers being sessile, or nearly so, and the clusters are called _verticillasters_ (fig. 17). Sometimes, especially towards the summit of a dichasium, owing to the exhaustion of the growing power of the plant, only one of the bracts gives origin to a new axis, the other remaining empty; thus the inflorescence becomes unilateral, and further development is arrested. In addition to the dichasial form there are others where more than two lateral axes are produced from the primary floral axis, each of which in turn produces numerous axes. To this form the terms _trichasial_ and _polychasial cyme_ have been applied; but these are now usually designated _cymose umbels_. They are well seen in some species of _Euphorbia_. Another term, _anthela_, has been used to distinguish such forms as occur in several species of _Luzula_ and _Juncus_, where numerous lateral axes arising from the primary axis grow very strongly and develop in an irregular manner.

FIG. 16.--Cymose inflorescence (dichasium) of _Cerastium collinum_; t-t"", successive axes. (After Duchartre.)]

In the uniparous cyme a number of floral axes are successively developed one from the other, but the axis of each successive generation, instead of producing a pair of bracts, produces only one. The basal portion of the consecutive axes may become much thickened and arranged more or less in a straight line, and thus collectively form an apparent or false axis or _sympodium_, and the inflorescence thus simulates a raceme. In the true raceme, however, we find only a single axis, producing in succession a series of bracts, from which the floral peduncles arise as lateral shoots, and thus each flower is on the same side of the floral axis as the bract in the axil of which it is developed; but in the uniparous cyme the flower of each of these axes, the basal portions of which unite to form the false axis, is situated on the opposite side of the axis to the bract from which it apparently arises (fig. 18). The bract is not, however, the one from which the axis terminating in the flower arises, but is a bract produced upon it, and gives origin in its axil to a new axis, the basal portion of which, constituting the next part of the false axis, occupies the angle between this bract and its parent axis--the bract from which the axis really does arise being situated lower down upon the same side of the axis with itself. The uniparous cyme presents two forms, the _scorpioid_ or _cicinal_ and the _helicoid_ or _bostrychoid_.

FIG. 18.--Helicoid cyme of a species of _Alstroemeria_. a1, a2, a3, a4, &c., separate axes successively developed in the axils of the corresponding bracts b2, b3, b4, &c., and ending in a flower f2, f3, f4, &c. The whole appears to form a simple raceme of which the axes form the internodes.

FIG. 19.--Scorpioidal or cicinal cyme of Forget-me-not (_Myosotis palustris_).

FIG. 20.--Diagram of definite floral axes a, b, c, d, e, &c.

FIG. 21.--Flowering stalk of Ragwort (_Senecio_). The flowers are in heads (capitula), and open from the circumference inwards in an indefinite centripetal manner. The heads of flowers, on the other hand, taken collectively, expand centrifugally--the central one a first.]

In the scorpioid cyme the flowers are arranged alternately in a double row along one side of the false axis (fig. 19), the bracts when developed forming a second double row on the opposite side; the whole inflorescence usually curves on itself like a scorpion's tail, hence its name. In fig. 20 is shown a diagrammatic sketch of this arrangement. The false axis, a b c d, is formed by successive generations of unifloral axes, the flowers being arranged along one side alternately and in a double row; had the bracts been developed they would have formed a similar double row on the opposite side of the false axis; the whole inflorescence is represented as curved on itself. The inflorescence in the family Boraginaceae are usually regarded as true scorpioid cymes.

In the helicoid cyme there is also a false axis formed by the basal portion of the separate axes, but the flowers are not placed in a double row, but in a single row, and form a spiral or helix round the false axis. In _Alstroemeria_, as represented in fig. 18, the axis a1 ends in a flower (cut off in the figure) and bears a leaf. From the axil of this leaf, that is, between it and the primary axis a1 arises a secondary axis a2, ending in a flower f2, and producing a leaf about the middle. From the axil of this leaf a tertiary floral axis a3, ending in a flower f3, takes origin. In this case the axes are not arranged in two rows along one side of the false axis, but are placed at regular intervals, so as to form an elongated spiral round it.

Compound definite inflorescences are by no means common, but in _Streptocarpus polyanthus_ and in several calceolarias we probably have examples. Here there are _scorpioid cymes of pairs of flowers_, each pair consisting of an older and a younger flower.

Mixed inflorescence.

Forms of inflorescence occur, in which both the definite and indefinite types are represented--_mixed_ inflorescences. Thus in Composite plants, such as hawk weeds (_Hieracia_) and ragworts (_Senecio_, fig. 21), the _heads_ of flowers, taken as a whole, are developed centrifugally, the terminal head first, while the _florets_, or small flowers on the receptacle, open centripetally, those at the circumference first. So also in Labiatae, such as dead-nettle (_Lamium_), the different whorls of inflorescence are developed centripetally, while the florets of the verticillaster are centrifugal. This mixed character presents difficulties in such cases as Labiatae, where the leaves, in place of retaining their ordinary form, become bracts, and thus might lead to the supposition of the whole series of flowers being one inflorescence. In such cases the cymes are described as spiked, racemose, or panicled, according to circumstances. In _Saxifraga umbrosa_ (London-pride) and in the horse-chestnut we meet with a raceme of scorpioid cymes; in sea-pink, a capitulum of contracted scorpioid cymes (often called a glomerulus); in laurustinus, a compound umbel of dichasial cymes; a scorpioid cyme of capitula in _Vernonia scorpioides_. The so-called catkins of the birch are, in reality, spikes of contracted dichasial cymes. In the bell-flower (_Campanula_) there is a racemose uniparous cyme. In the privet (_Ligustrum vulgare_) there are numerous racemes of dichasia arranged in a racemose manner along an axis; the whole inflorescence thus has an appearance not unlike a bunch of grapes, and has been called a _thyrsus_.

TABULAR VIEW OF INFLORESCENCES

A. Indefinite Centripetal Inflorescence.
I. Flowers solitary, axillary. _Vinca_, _Veronica hederifolia_.
II. Flowers in groups, pedicellate.
1. Elongated form (Raceme), _Hyacinth_, _Laburnum_, _Currant_.
(Corymb), _Ornithogalum_.
2. Contracted or shortened form (Umbel), _Cowslip_,
_Astrantia_.
III. Flowers in groups, sessile.
1. Elongated form (Spike), _Plantago_.
(Spikelet), _Grasses_.
(Amentum, Catkin), _Willow_, _Hazel_.
(Spadix) _Arum_, some _Palms_.
(Strobilus), _Hop_.
2. Contracted or shortened form (Capitulum), _Daisy_,
_Dandelion_, _Scabious_.
IV. Compound Indefinite Inflorescence.
a. Compound Spike, _Rye-grass_.
b. Compound Spadix, _Palms_.
c. Compound Raceme, _Astilbe_.
d. Compound Umbel, _Hemlock_ and most _Umbelliferae_.
e. Raceme of Capitula, _Petasites_.
f. Raceme of Umbels, _Ivy_.
B. Definite Centrifugal Inflorescence.
I. Flowers solitary, terminal. _Gentianella_, _Tulip_.
II. Flowers in Cymes.
1. Uniparous Cyme.
a. Helicoid Cyme (axes forming a spiral).
Elongated form, _Alstromeria_.
Contracted form, _Witsenia corymbosa_.

b. Scorpioid Cyme (axes unilateral, two rows).
Elongated form, _Forget-me-not_, _Symphytum_,
_Henbane_.
Contracted form, _Erodium_, _Alchemilla arvensis_.
2. Biparous Cyme (Dichotomous), including 3-5 chotomous
Cymes (Dichasium, Cymose Umbel, Anthela).
a. Elongated form, _Cerastium_, _Stellaria_.
b. Contracted form (Verticillaster), _Dead-nettle_,
_Pelargonium_.
3. Compound Definite Inflorescence. _Streptocarpus
polyanthus_, many _Calceolarias_.
C. Mixed Inflorescence.
Raceme of Scorpioid Cymes, _Horse-chestnut_.
Scorpioid Cyme of Capitula, _Vernonia scorpioides_.
Compound Umbel of Dichotomous Cymes, _Laurustinus_.
Capitulum of contracted Scorpioid Cymes (Glomerulus),
_Sea-pink_.

FIG. 22.--Flower of _Sedum rubens_. s, Sepals; p, petals; a, stamens; c, carpels.

FIG. 23.--Diagram of a completely symmetrical flower, consisting of four whorls, each of five parts, s, Sepals; p, petals; a, stamens; c, carpels.

FIG. 24.--Monochlamydeous (apetalous) flower of Goosefoot (_Chenopodium_), consisting of a single perianth (calyx) of five parts, enclosing five stamens, which are opposite the divisions of the perianth, owing to the absence of the petals.

FIG. 25.--Stamen, consisting of a filament (stalk) f and an anther a, containing the pollen p, which is discharged through slits in the two lobes of the anther.

FIG. 26.--The pistil of Tobacco (_Nicotiana Tabacum_), consisting of the ovary o, containing ovules, the style s, and the capitate stigma g. The pistil is placed on the receptacle r, at the extremity of the peduncle.]

The flower.