Chapter XV: Part 15

The contrast presented by the physiognomy of the Casuarineas,
acicular-leaved trees, and the almost leafless Peruvian Colletias and
Pothos plants (Aroideas), is still more striking when we compare these
types of extreme contraction in the leaf form with Nymphæaceæ and
Nelumboneæ. Here we again meet, as in the Aroideæ, with leaves in
which the cellular tissue is excessively expanded upon long, fleshy,
succulent petioles,—as Nymphæa alba, N. lutea, N. thermalis (formerly
called N. lotus, from the hot spring of Pecze, near Groswardein in
Hungary), the species of Nelumbo, Euryale amazonica (Pöppig), and
Victoria Regina, allied to the prickly Euryale, although of a very
different genus, according to Lindley, and discovered in 1837 by Sir
Robert Schomburgk in the river Berbice, in British Guiana. The round
leaves of this splendid aquatic plant are from 5 to 6 feet in
diameter, and surrounded by upright margins from 3 to 5 inches in
height, which are light green on the inner side, but of a bright
crimson on the outside. These agreeably perfumed flowers, of which 20
or 30 may be seen together in a small space, are about 15 inches in
diameter, of a white or rose colour, and have many hundred petals.[QA]
Pöppig also gives to the leaves of his Euryale amazonica, which he
found at Tefé, a diameter of about 6 feet.[QB] Whilst Euryale and
Victoria present a greater parenchymatous expansion of the leaf-form
in all its dimensions than other genera, the most gigantic development
of the blossoms occurs in a parasitical Cytinea, which Dr. Arnold
discovered in Sumatra in 1818. This flower, Rafflesia Arnoldi (R.
Brown), has a stemless blossom measuring three feet in diameter,
surrounded by large leaf-like scales. Like funguses, it has an animal
odour, and smells something like beef.

Footnote 95:

p. 227—“_Lianes, Creeping Plants, (Span. Vejuccos.)_”

According to Kunth’s division of Bauhinias, the true genus Bauhinia
belongs to the New Continent. The African Bauhinia, B. rufescens
(Lam.), is a Pauletia (Cav.), a genus of which we also discovered some
new species in South America. In the same manner the Banisterias of
the Malpighiaceæ are actually an American form. Two species are
indigenous to the East Indies, and one—described by Cavanilles as B.
leona—to Western Africa. In the tropical zone, and in the Southern
hemisphere, species of the most different families belong to the
climbing plants which in those regions render the forests so
impenetrable to man and so accessible and habitable to the whole
monkey family (Quadrumana), the Cercoleptes, and the small tiger cats.
The Lianes thus afford whole flocks of gregarious animals an easy
means of rapidly ascending high trees, passing from one tree to
another, and even of crossing brooks and rivulets.

In the south of Europe and in the north of America, Hops from the
Urticeæ, and the species of Vitis from the Ampelideæ, belong to
Climbing Plants; while this form is represented in the tropics by
climbing and trailing grasses. We found on the elevated plains of
Bogota, in the pass of Quindiu in the Andes, and in the Cinchona
forests of Loxa, a Bambusa allied to Nastus, our Chusquea scandens,
twined round powerful trunks of trees, adorned at the same time with
flowering Orchideæ. Bambusa scandens (Tjankorreh), which Blume found
in Java, belongs probably to Nastus, or to the grass-genus Chusquea,
the Carrizo of the Spanish settlers. In the pine forests of Mexico,
Climbing Plants seem to be entirely wanting; but in New Zealand a
fragrant Pandanus, Freycinetia Banksii, together with one of the
Smilaceæ, Ripogonum parviflorum (R. Brown), which renders the forests
almost impenetrable, winds round a gigantic fir-tree more than 200
feet high, Podocarpus dacryoides (Rich.), called Kakikatea in the
language of the country.[QC]

A striking contrast to these Climbing Grasses and Creeping Pandaneas
is afforded by the splendid many-coloured blossoms of the Passion
flowers (among which, however, we ourselves found one arborescent,
upright, species (Passiflora glauca) in the Andes of Popayan, at an
elevation of nearly 10,500 feet, and by the Bignoniaceæ, Mutisiæ,
Alströmeriæ, Urvilleæ, and Aristolochiæ. Among the latter, our
Aristolochia cordata has a coloured (purplish red) calyx, about
seventeen inches in diameter; “flores gigantei, pueris mitræ instar
inservientes.” Owing to the quadrangular form of their stalks, their
flattening, which is not occasioned by any external pressure, and a
band-like undulatory motion, many of these climbing plants have a
peculiar physiognomy. The diagonal intersections of the stems of
Bignonias and Banisterias form, by means of furrows in the ligneous
substance, and through its clefts, where the bark penetrates to some
depth, cruciform or mosaic-like figures.[QD]

Footnote 96:

p. 228—“_The form of Aloes_.”

To this group of plants, which is characterised by a great similarity,
belong Yucca aloifolia, which penetrates as far north as Florida and
South Carolina; Y. angustifolia (Nutt.), which advances to the banks
of the Missouri; Aletris arborea; the Dragon-tree of the Canaries, and
two other Dracænas belonging to New Zealand; arborescent Euphorbias;
and Aloe dichotoma, Linn., (formerly the genus Rhipidodendrum of
Willdenow), the celebrated Koker-boom, whose stem is four feet in
thickness, about twenty feet high, and has a crown measuring 426 feet
round.[QE] The forms which I have here associated together belong to
very different families: as, for instance, to the Liliaceæ,
Asphodeleæ, Pandaneæ, Amaryllideæ, and Euphorbiaceæ; and are
therefore, with the exception of the last named, all included under
the great division of Monocotyledons. One of the Pandaneæ, Phytelephas
macrocarpa (Ruiz), which we found on the banks of the Magdalena river
in New Granada, exactly resembles with its feathery leaves a small
palm-tree. The Tagua (as it is called by the Indians) is moreover, as
Kunth has observed, the only Pandanea of the New Continent. The
singular Agave-like and high-stemmed Doryanthes excelsa of New South
Wales, which the intelligent Correa de Serra was the first to
describe, belongs to the Amaryllideæ, like our low-growing Narcissuses
and Jonquils.

In the candelabra-like form of Aloes, the branches of the main-trunk
must not be confounded with the flower-stalks. In the American aloe,
Agave Americana (Maguey de Cocuyza), which is entirely wanting in
Chili, and in the Yucca acaulis (Maguey de Cocuyza), the leaf-stalks
present a candelabra-like arrangement of the blossoms during the
excessively rapid and gigantic development of the inflorescence,
which, as is well known, is but too transient a phenomenon. In some
arborescent Euphorbias the physiognomical character depends, however,
on the branches and their arrangement. Lichtenstein describes,[QF]
with much animation, the impression made upon him by the appearance of
an Euphorbia officinarum which he saw in the “Chamtoos Rivier,” near
Cape Town. The form of the tree was so symmetrical, that it repeated
itself on a small scale, like a candelabrum, to a height of more than
30 feet. All the branches were furnished with sharp thorns.

Palms, Yucca and Aloe plants, arborescent Ferns, some Aralias, and the
Theophrasta, where I have seen it in a state of luxuriant growth,
present to the eye a certain physiognomical resemblance of character
by the nakedness of the stems (there being no branches) and the beauty
of their summits or crowns, however they may otherwise differ in the
structure of the inflorescence.

Melanoselinum decipiens, (Hofm.), which has been introduced into our
gardens from Madeira, and is sometimes from 10 to 12 feet high,
belongs to a peculiar group of arborescent umbelliferæ allied to the
Araliaceæ, to which other species, as yet undiscovered, will
undoubtedly at some future time be added. Ferula, Heracleum, and
Thapsia likewise attain a considerable height, but they are still
herbaceous shrubs. Melanoselinum stands almost entirely alone as an
arborescent umbelliferous plant; Bupleurum (_Tenoria_) fruticosum,
Linn., of the shores of the Mediterranean, Bubon galbanum of the Cape,
and Crithmum maritimum of our sea-coasts, are only shrubs. Tropical
countries, where, as Adanson long since very correctly remarked,
Umbellifereæ and Crucifereæ are almost wholly wanting in the plains,
exhibit, as we ourselves observed, the most dwarfish of all the
umbelliferous family on the lofty mountain ridges of the South
American and Mexican Andes. Among the thirty-eight species which we
collected on elevations whose mean temperature was below 54°.5 Fahr.,
we found Myrrhis andicola, Fragosa arctioïdes, and Pectophytum
pedunculare, interspersed with an equally dwarfish Alpine Draba,
growing moss-like close to the rock and the frequently frozen earth,
at a height of 13,428 feet above the level of the sea. The only
tropical umbelliferous plants which we found on the plain in the New
Continent were two species of Hydrocotyle (_H. umbellata_ and _H.
leptostachya_) between the Havannah and Batabano, and therefore at the
extreme limit of the torrid zone.

Footnote 97:

p. 228—“_The form of Grasses_.”

The group of the arborescent grasses which Kunth has collected under
the head of Bambusaceæ, in his great work on the plants collected by
Bonpland and myself, constitutes one of the most beautiful adornments
of tropical vegetation. Bambu, called also Mambu, occurs in the Malay
language, although according to Buschmann merely as an isolated
expression, the ordinary term in use being buluh, whilst the only name
for this species of cane in Java and Madagascar is wuluh, voulou. The
numbers of the genera and species included in this group have been
extraordinarily increased by the industry of botanical travellers. It
has been found that the genus Bambusa is entirely wanting in the New
Continent, to which region, however, the gigantic Guaduas, discovered
by us, and which attain a height of from 50 to 64 feet, together with
the Chusquea, exclusively belong; that Arundinaria (Rich.) occurs in
both continents, although differing specifically in each; that Bambusa
and Beesha (Rheed.), occur in India and the Indian Archipelago; and
that Nastus grows in the islands of Madagascar and Bourbon. With the
exception of the high-climbing Chusquea, these forms morphologically
replace each other in different parts of the earth. In the northern
hemisphere far beyond the limits of the torrid region, in the valley
of the Mississippi, the traveller is gladdened by the sight of a
species of Bamboo, the Arundinaria macrosperma, formerly called also
Miegia and Ludolfia. In the southern hemisphere, in the south of
Chili, between the parallels of 37° and 42°, Gay found one of the
Bambusaceæ more than 20 feet high (not a climbing, but a still
undescribed arborescent self-supporting Chusquea), growing, mingled
with Drymis Chilensis, in a region clothed with an uniform
forest-covering of Fagus obliqua.

Whilst in India the Bambusa flowers so frequently that in Mysore and
Orissa the seeds are mixed with honey, and eaten like rice,[QG] in
South America the Guadua blossoms so very seldom that in the course of
four years we were only twice able to procure the flowers; once on the
solitary banks of the Cassiquiare, the arm connecting the Orinoco with
the Rio Negro and the Amazon, and again in the province of Popayan,
between Buga and Quilichao. It is a very striking fact that some
plants grow with the greatest vigour in certain localities without
flowering; as is the case with the European olive-trees introduced
into America centuries ago, and growing between the tropics, near
Quito, at elevations of about 9600 feet above the level of the sea;
and in like manner the walnuts, hazel-nut bushes, and the fine
olive-trees (_Olea Europea_) of the Isle of France.[QH]

As some of the Bambusaceæ (arborescent grasses) advance into the
temperate zone, so also they do not suffer in the torrid zone from the
temperate climate of mountain districts. They are certainly more
luxuriant as social plants between the sea-shore and elevations of
about 2558 feet in the Province de las Esmeraldas, west of the volcano
of Pichincha, where Guadua angustifolia (Bambusa Guadua of our
_Plantes équinoxiales_, t, i. tab. xx) generates in its interior large
quantities of the siliceous Tabaschir (Sanscrit _tvakkschira_,
cow-milk). We saw the Guadua advance in the pass of Quindiu, in the
chain of the Andes, to a height of 5755 feet above the level of the
sea, as determined by barometric measurements. Nastus borbonicus has
been called a true Alpine plant by Bory de St. Vincent, and according
to him it does not descend lower than 3840 feet on the declivity of
the volcano in the island of Bourbon. This appearance or the
repetition at great elevations of certain forms belonging to torrid
plains calls to mind the group of Alpine palms (Kunthia montana,
Ceroxylon andicola, and Oreodoxa frigida) of which I have already
spoken, and a grove of Musaceæ (Heliconia, perhaps Maranta), 16 feet
high, which I found growing isolated on the Silla de Caracas, at a
height of more than 7000 feet above the level of the sea.[QI] While
the form of gramineæ, with the exception of some few herbaceous
dicotyledons, constitutes the highest phanerogamic zone on the
snow-crowned summits of mountains, so the grasses mark the boundary of
phanerogamic vegetation in a horizontal direction, towards the
northern and southern polar regions.

Many admirable general results, no less than a great mass of important
materials, have been yielded to the geography of plants by my young
friend, Joseph Hooker, who, after having but recently returned with
Sir James Boss from the frozen antarctic regions, is now engaged in
exploring the Thibetian Himalaya. He draws attention to the fact that
phanerogamic flowering plants (grasses) advance 17½° nearer to the
north than to the south pole. In the Falkland Islands, near the thick
knots of Tussac grass, Dactylis cæspitosa, Forster. (a Festuca,
according to Kunth), and in Tierra del Fuego, under the shade of the
birch-leaved Fagus antarctica, there grows the same Trisetum
subspicatum, which spreads over the whole range of the Peruvian Andes,
and across the Rocky Mountains, to Melville Island, Greenland, and
Iceland, and is also found in the Swiss and Tyrolese Alps as well as
in the Altai, in Kamtschatka, and in Campbell’s Island, south of New
Zealand, extending therefore over 127 degrees of latitude, or from 54°
south to 72° 50′ north lat. “Few grasses,” says Joseph Hooker,[QJ]
“have so wide a range as Trisetum subspicatum (Beauv.), nor am I
acquainted with any other arctic species which is equally an
inhabitant of the opposite polar regions.” The South Shetland Islands,
which are separated by Bransfield Straits from d’Urville’s “Terre de
Louis-Philippe” and from Peak Haddington, a volcano, 7046 feet high,
and situated in 64° 12′ south lat., have recently been visited by Dr.
Eights, a botanist from the United States. He found there (probably in
62° or 62¼° south lat.) a small grass, Aira antarctica,[QK] which is
“the most antarctic flowering plant hitherto discovered.”

Even in Deception Island, belonging to the same group, 62° 50′, only
lichens are met with, and no longer any species of grass; and in like
manner further south-east, in Cockburn’s Island (64° 12′) near
Palmer’s Land, only Lecanoras, Lecideas, and five foliaceous Mosses,
among which is our German Bryum argenteum, were gathered. “This
appears to be the Ultima Thule of antarctic vegetation,” for further
south even terrestrial cryptogamia are wanting. In the great bay
formed by Victoria Land, on a small island lying opposite to Mount
Herschel (in 71° 49′ lat.), and on Franklin Island, 92 miles north of
the volcano, Erebus, (12,366 feet in height), and in 76° 7′ south
lat., Hooker found no trace of vegetation. In extreme northern
latitudes, the distribution of even the higher organisms is very
different; for here phanerogamic plants advance 18½° nearer to the
pole than in the southern hemisphere. Walden Island (80½° north lat.)
possesses still ten species of phanerogamia. Antarctic phanerogamic
vegetation is also poorer in species at equal distances from the pole;
thus Iceland has five times more phanerogamia than the southern group
of Auckland and Campbell Islands, but the uniform vegetation of the
antarctic regions is, from climatic causes, both more succulent and
more luxuriant.[QL]

Footnote 98:

p. 229—“_Ferns_.”

If we estimate the whole number of the cryptogamia hitherto described
at 19,000 species, as has been done by Dr. Klotzsch, a naturalist
possessing a profound acquaintance with the Agamic plants, we shall
have for Fungi 8000 (of which Agarici constitute the eighth part); for
Lichens, according to J. von Flotow of Hirschberg, and Hampe of
Blankenburg, at least 1400; for the Algæ 2580; for Mosses and
Liverworts, according to Carl Müller of Halle, and Dr. Gottsche of
Hamburgh, 3800; and for Ferns 3250. For this last important result we
are indebted to the profound investigations made by Professor Kunze of
Leipzig, on this group of plants. It is a striking fact that the
family of the Polypodiaceæ alone includes 2165 of the whole number of
described Filices, whilst other forms, as the Lycopodiacæ and
Hymenophyllaceæ, number only 350 and 200. There are therefore nearly
as many described species among Ferns as among Grasses.

It is singular that no mention of the beautiful arborescent ferns is
to be found in the classic authors of antiquity, Theophrastus,
Dioscorides, and Pliny; while, from the information given by the
companions of Alexander, Aristobulus, Megasthenes, and Nearchus,
reference is made[QM] to Bamboos, “quæ fissis internodiis lembi vice
vectitabant navigates;” to the Indian trees “quarum folia non minora
clypeo sunt;” to the Fig-tree which takes root from its branches, and
to Palms, “tantæ proceritatis, ut sagittis superjici nequeant.” I find
the first mention of arborescent ferns in Oviedo.[QN] “Among ferns,”
says this experienced traveller, who had been appointed by Ferdinand
the Catholic, Director of the Goldwashings in Haiti, “there are some
which I class with trees, because they are as thick and high as
Pine-trees. (Helechos que yo cuento por arboles, tan gruesos como
grandes pinos y muy altos). They mostly grow among the mountains and
where there is much water.” This estimate of their height is
exaggerated, for in the dense forests near Caripe even our Cyathea
speciosa only attains a height of 32 to 37 feet; and an admirable
observer, Ernst Dieffenbach, did not see in the most northern of the
three islands of New Zealand any trunks of Cyathea dealbata exceeding
42½ feet. In the Cyathea speciosa and the Meniscium of the Chaymas
missions, we observed in the midst of the most shady part of the
primeval forest, that the scaly stems of some of the most luxuriantly
developed of these trees were covered with a shining carbonaceous
powder, which appeared to be owing to a singular decomposition of the
fibrous parts of the old leaf stalks.[QO]

Between the tropics, where, on the declivities of the Cordilleras,
climates are superimposed in strata, the true region of arborescent
ferns lies between about 3200 and 5350 feet above the level of the
sea. In South America and in the Mexican highlands they seldom descend
lower towards the plains than 1280 feet. The mean temperature of this
happy region is between 64°.6 and 70°.8 Fahr. It reaches the lowest
stratum of clouds (which floats the nearest to the surface of the sea
and the plain), and it therefore enjoys uninterruptedly a high degree
of humidity, together with a great equality in its thermal
relations.[QP] The inhabitants, who are of Spanish descent, call this
region “Tierra templada de los helechos.”

The Arabic designation for ferns is _feledschun_, filix, (from which
the _f_ has been changed, according to Spanish usage, into _h_,) and
perhaps the term may be connected with the verb _faladscha_, “it
divides,” from the finely cut margin of the frond.[QQ]

The conditions of genial mildness in an atmosphere charged with
aqueous vapour and of great uniformity in respect to moisture and
warmth, are fulfilled on the declivities of the mountains in the
valleys of the Andes, and more especially in the southern milder and
more humid hemisphere, where arborescent ferns advance not only to New
Zealand and Van Diemen’s Land (Tasmania), but even as far as the
Straits of Magellan and Campbell Island, and therefore to a southern
latitude almost identical in degrees with the parallel in which Berlin
is situated north of the equator. From among the family of arborescent
ferns there flourishes the vigorous Dicksonia squarrosa, in 46° south
lat. in Dusky Bay, New Zealand; D. antarctica of Labillardière in
Tasmania; a Thyrsopteris in the Island of Juan Fernandez; an
undescribed Dicksonia, whose stem is from 12 to 16 feet high, near
Valdivia in Southern Chili; and a Lomaria, somewhat less in height, in
the Straits of Magellan. Campbell Island is still nearer to the south
pole, in 52½° lat., but even there the leafless stem of the Aspidium
venustum rises to a height of more than four feet.

The climatic relations under which Ferns (_Filices_) in general
flourish, are manifested in the numerical laws of their quotients of
distribution. In the plains within the tropical regions of large
continents this quotient is, according to Robert Brown, and from more
recent investigations on the subject, ¹⁄₂₀ of all the phanerogamia,
and in mountainous districts of large continents ⅙ to ⅛. This ratio is
quite different on the small islands scattered over the ocean; for
here the proportion borne by the number of ferns to the sum total of
all the phanerogamic plants increases so considerably, that in the
South-Sea Islands the quotient rises to ¼, while in the sporadic
islands, St. Helena and Ascension, the number of ferns is almost equal
to half of the whole phanerogamic vegetation.[QR] In receding from the
tropics (where on the large continents d’Urville estimates the
proportional number at ¹⁄₂₀), the _relative_ frequency of ferns
decreases rapidly as we advance into the temperate zone. The quotients
are for North America and the British Islands ¹⁄₃₅, for France ¹⁄₅₈,
for Germany ¹⁄₅₂, for the dry parts of Southern Italy ¹⁄₇₄, for Greece
¹⁄₈₄. The _relative_ frequency again increases considerably towards
the frigid north. Here the family of ferns decreases much slower in
the number of its species than does that of phanerogamic plants. The
luxuriantly aspiring character of the species, and the number of
individuals contained in each, augment the deceptive impression of
_absolute_ frequency. According to Wahlemberg’s and Hornemann’s
catalogues, the relative numbers of the Filices are for Lapland ¹⁄₂₅,
for Iceland ¹⁄₁₈, for Greenland ¹⁄₁₂.

Such are, according to our present knowledge, the natural laws that
manifest themselves in the distribution of the graceful form of Ferns.
But it would seem as if in the family of Ferns, which have so long
been regarded as cryptogamic, we had lately acquired evidence of the
existence of another natural law,—the morphological law of
propagation. Count Leszczyc-Suminski, who happily combines the power
of microscopic investigation with a very remarkable artistic talent,
has discovered an organisation capable of effecting fructification in
the prothallium of ferns. He distinguishes two sexual apparatuses, of
which the female portion is situated in hollow ovate cells in the
middle of the sporangium, and the male in the ciliated antheridia, or
the organs producing spiral threads, which have already been examined
by Nägeli. Fructification is supposed to be effected by means of
moveable ciliated spiral threads and not by pollen tubes.[QS]
According to this view, Ferns would be, as Ehrenberg remarks,[QT]
products of a microscopic fructification taking place on the
prothallium, which here serves as a fertilizing receptacle, while
throughout the whole course of their often arborescent development
they would be flowerless and fruitless plants, having a bud-formation.
The spores lying as sori on the under side of the frond are not seeds
but flower-buds.

Footnote 99:

p. 229—“_The Liliaceæ_.”

Africa is the principal seat of this form; there the greatest
diversity obtains; there they form masses and determine the natural
character of the region. The New Continent exhibits also, it is true,
magnificent Alströmeriæ and species of Pancratium, Hæmanthus, and
Crinum. We have enriched the first of these genera with nine, and the
second with three species; but these American liliaceous plants are
more diffused and of less social habits than the European Irideæ.

Footnote 100:

p. 229—“_The Willow Form_.”

Nearly 150 different species of the main representatives of this form,
or rather of the Willow itself, are already known. They cover the
northern parts of the earth from the equator to Lapland. Their number
and their varieties of form increase between the 46th and 70th degrees
of latitude, more especially in that part of northern Europe which has
been so remarkably indented by the early revolutions of our planet. I
am acquainted with ten or twelve species of inter-tropical Willows,
and these, like the Willows of the southern hemisphere, are deserving
of special attention. As nature appears to delight in all zones in a
wondrous multiplication of certain animal forms, as for instance,
Anatidæ (_Lamellirostres_), and Pigeons; so likewise are Willows,
Pines, and Oaks, widely diffused; the latter always exhibiting a
similarity in their fruit, although various differences exist in the
form of the leaves. In Willows belonging to the most widely different
climates the similarity of the foliage, of the ramification, and of
the whole physiognomical conformation, is almost greater than in
Coniferæ. In the more southern part of the temperate zone, north of
the equator, the number of the species of Willows decreases
considerably; although (according to the “Flora atlantica” of
Desfontaines) Tunis has still its own species, resembling Salix
caprea; whilst Egypt, according to Forskäl, numbers five species, from
the catkins of whose male blossoms is distilled the remedial agent
Moie chalaf (_aqua salicis_), so much used in the East. The Willow
which I saw in the Canaries is also, according to Leopold von Buch and
Christian Smith, a peculiar species (_S. canariensis_), although
common to those islands and to Madeira. Wallich’s catalogue of the
plants of Nepaul and the Himalaya already gives 13 species belonging
to the subtropical zone of the East Indies, and which have in part
been described by Don, Roxburgh, and Lindley. Japan has its own
species, of which one, S. japonica. (Thunb.), is also met with in
Nepaul as an Alpine plant.

There was not, as far as I am aware, any species of Willow known as
belonging to the tropical zone before my expedition, with the
exception of S. tetrasperma. We collected seven new species, three of
them on the plateaux of Mexico, at an elevation of 8500 feet above the
level of the sea. Still higher, as for instance on the Alpine plains,
between 12,000 and 15,000 feet, which we frequently visited, we saw
nothing in the Andes of Mexico, Quito, and Peru, to remind us of the
many small creeping Alpine Willows of the Pyrenees, the Alps, or of
Lapland (_S. herbacea_, _S. lanata_, and _S. reticulata_). In
Spitzbergen, whose meteorological relations have so much analogy with
those of the snow-crowned summits of Switzerland and Scandinavia,
Martius described two Dwarf-Willows, whose small woody stems and
branches trail along the ground, and are so concealed in the turf-bogs
that it is with difficulty their diminutive leaves can be discovered
under the moss. The Willow species which I found in 4° 12′ south lat.,
at the entrance of the Cinchona or Peruvian Bark forests, near Loxa in
Peru, and which has been described by Willdenow as Salix Humboldtiana,
is most widely diffused over the western part of South America. A
Beach-Willow (_S. falcata_), which we discovered on the sandy shores
of the Pacific, near Truxillo, is, according to Kunth, probably a mere
variety of the former. In like manner the beautiful and frequently
pyramidal Willow, which we constantly saw on the banks of the
Magdalena river, from Mahates to Bojorque, and which, according to the
report of the natives, had only spread thus far within a few years,
may also be identical with S. Humboldtiana. At the confluence of the
Magdalena with the Rio Opon, we found all the islands covered with
Willows, many of which had stems 64 feet high, with a diameter of from
only 8 to 10 inches.[QU] Lindley has made us acquainted with a species
of Salix belonging to Senegal, and therefore to the equinoctial region
of Africa.[QV] Blume also found two species of Willow near the equator
in Java, one wild and indigenous in the island (_S. tetrasperma_), and
another cultivated (_S. Sieboldiana_). I am only acquainted with the
two Willows belonging to the south temperate zone, which have been
described by Thunberg (_S. hirsuta_ and _S. mucronata_). They grow
interspersed with Protea argentea, which has the same physiognomy as
the Willow, and their leaves and young branches constitute the food of
the hippopotamus of the Orange River. The family of Willows is
entirely wanting in Australia and the neighbouring islands.

Footnote 101:

p. 229—“_The Myrtle Form_.”

The Myrtle is a graceful plant, with stiff, shining, crowded, and
generally entire and small leaves marked with dots. Myrtles impart a
peculiar character to three regions of the earth, viz., to southern
Europe, more especially to the islands composed of calcareous rocks
and trachytic stone, which project from the basin of the
Mediterranean; to the continent of New Holland, which is adorned with
Eucalyptus, Metrosideros, and Leptospermum; and to an inter-tropical
region in the Andes of South America, part of which is a low plain,
while the remainder lies at an elevation of from 9000 to more than
10,000 feet above the level of the sea. This Alpine region, called in
Quito the Paramos, is entirely covered with trees having a Myrtle-like
aspect, even though they may not all belong to the Myrtaceæ. At this
elevation grow Escalonia myrtilloides, E. tubar, Simplocos Alstonia,
species of Myrica, and the lovely Myrtus microphylla, of which we have
given a drawing in our _Plantes équinoxiales_, t. i. p. 21, pl. iv.;
it grows on micaceous schist, at an elevation of 10,000 feet on the
Paramo de Saraguru, (near Vinayacu and Alto de Pulla,) which is
adorned with so many beautiful flowering Alpine plants. M. myrsinoides
ascends in the Paramo de Guamani as high as 11,200 feet. By far the
greater number of the 40 species of the genus Myrtus which we
collected in the equinoctial zone, and of which 37 were undescribed,
belong to the plains and the less elevated mountain spurs. We brought
only a single species (_M. xalapensis_) from the mild tropical climate
of the mountains of Mexico; but the Tierra templada, in the direction
of the Volcano of Orizaba, no doubt possesses many yet undescribed
varieties. We found M. maritima near Acapulco, on the very shore of
the Pacific.

The _Escalloniæ_,—among which _E. myrtilloides_, _E. tubar_, _E.
floribunda_ are the ornaments of the Paramos, and remind us strongly
(by their physiognomical aspect) of the myrtle-form,—formerly
constituted, together with the European and South American Alpine
roses (Rhododendrum and Befaria), with Clethra, Andromeda, and
Gaylussacia buxifolia, the family of the _Ericeæ_. Robert Brown[QW]
has arranged them in a special family, which Kunth has placed between
the Philadelphiæ and Hamamelideæ. Escallonia floribunda affords by its
geographical distribution one of the most striking examples of the
relation existing between distance from the equator and vertical
elevation above the level of the sea. I would here again borrow
support from the testimony of the accurate observer, my friend Auguste
de St. Hilaire.[QX] “MM. Humboldt and Bonpland in their expedition
discovered Escallonia floribunda in 4° south lat. at an elevation of
8952 feet. I found the same plant in 21° south lat. in Brazil, which
although elevated is very much less so than the Andes of Peru. This
plant is of common occurrence between 24° 50′ and 25° 55′ in the
Campos Geraes, and I also met with it again on the Rio de la Plata in
about 35° lat., on a level with the sea.”

The group of the Myrtaceæ,—to which belong Melaleuca, Metrosideros,
and Eucalyptus, commonly classed under the general denomination of
Leptospermeæ,—produce partially, wherever the true leaves are supplied
by phyllodia (petiole-leaves), or where the direction of the leaves is
inclined towards the unexpanded petiole, a distribution of streaks of
light and shade wholly unknown in our deciduous-leaved forest. We find
that the earliest botanical travellers who visited New Holland were
astonished at the singular effect thus produced. Robert Brown was the
first to show that this phenomenon depends on the vertical direction
of the expanded petioles (the phyllodia of Acacia longifolia and
Acacia suaveolens), and on the circumstance, that the light, instead
of falling on horizontal surfaces, passes between vertical ones.[QY]
Morphological laws in the development of the leaves determine the
peculiar character of the varying light and shade. “Phyllodia,” says
Kunth, “can in my opinion merely occur in families which have compound
pinnate leaves; and in fact they have as yet only been met with in
Leguminosæ (in the Acacias). In Eucalyptus, Metrosideros, and
Melaleuca, the leaves are simple (simplicia), and their edgewise
position depends on a half-turn of the leaf-stalk (petiolus);
moreover, it must be remarked, that both surfaces of the leaves are of
a similar character.” In the scantily shaded forests of New Holland
the optical effects here alluded to are the more frequent, since two
groups of Myrtaceæ and Leguminosæ, species of Eucalyptus and Acacia,
there constitute nearly one-half of all the greyish-green tree
vegetation. Moreover, between the bast-layers of Melaleuca, there are
formed easily soluble membranes, which force their way outwards, and
by their whiteness reminds us of our birch bark.

The sphere of distribution of the Myrtaceæ is very different in the
two continents. In the New Continent, and especially in its western
parts, this family, according to Joseph Hooker,[QZ] scarcely extends
beyond the parallel of 26° north lat., while in the Southern
Hemisphere, there are in Chili, according to Claude Gay, ten species
of Myrtle and twenty-two of Eugenia, which mixed with Proteaceæ
(Embothrium and Lomatia) and with Fagus obliqua, there constitute
forests. The Myrtaceæ become more frequent from the 38th degree of
south lat.; in the island of Chiloe, where a metrosideros-like species
(Myrtus stipularis) forms almost impenetrable underwood, which is
there named Tepuales; and in Patagonia to the extremity of Tierra del
Fuego in 56° lat. While in Europe the Myrtaceæ do not extend northward
further than 46° lat., they penetrate in Australia, Tasmania, New
Zealand and the Auckland Islands to 50½° south latitude.

Footnote 102:

p. 229—“_Melastomaceæ_.”

This group comprises the genera Melastoma (Fothergilla and Tococa Aub.
and Rhexia (Meriana and Osbeckia), of which we have collected no less
than sixty new species in tropical America alone, on both sides of the
equator. Bonpland has published a splendid work on the Melastomaceæ,
in two volumes, with coloured plates. There are species of Rhexia and
Melastoma which ascend in the chain of the Andes, as Alpine or Paramos
shrubs, to 9600 and even more than 11,000 feet above the level of the
sea; as for instance Rhexia cernua, R. stricta, Melastoma obscurum, M.
aspergillare, and M. lutescens.

Footnote 103:

p. 229—“_The Laurel-form_.”

To this form belong Laurus, Persea, the Ocoteæ, so numerous
in South America, and,—on account of their physiognomic
similarity,—Calophyllum, also the splendidly aspiring Mammea from the
Guttiferæ.

Footnote 104:

p. 229—“_How instructive to the landscape-painter would be a work
which should illustrate the leading forms of vegetation_.”

In order to define with more distinctness what I have here only
briefly referred to, I may be permitted to incorporate the following
considerations from my sketch of a history of landscape painting, and
of a graphical representation of the physiognomy of plants.[RA]

“All that relates to the expression of the passions and the beauty of
the human form has perhaps attained its fullest development in the
temperate northern zone under the skies of Greece and Italy. The
artist, drawing from the depths of imagination, no less than from the
contemplation of beings of his own species, derives the types of
historical painting alike from unfettered creation and from truthful
imitation. Landscape painting, though scarcely a more imitative art,
has a more material basis, and a more earthly tendency. It requires
for its development a greater amount of various and distinct
impressions, which, when imbibed from external contemplation, must be
fertilized by the powers of the mind in order to be presented to the
senses of others as a creative work of art. The grander style of
heroic landscape-painting is the combined result of a profound
appreciation of nature, and of this inward process of the mind.

“Everywhere, in every separate portion of the earth, nature is indeed
only a reflex of the whole. The forms of organization recur again and
again in different combinations. Even the icy north is cheered for
months together by the presence of herbs and large Alpine blossoms
covering the earth, and by a mild azure sky. Hitherto landscape
painting among us has pursued her graceful labours familiar only with
the simpler forms of our native floras, but not therefore without
depth of feeling and richness of creative fancy. Dwelling only on the
native and indigenous form of our vegetation, this branch of art,
notwithstanding that it has been circumscribed by such narrow limits,
has yet afforded sufficient scope for highly-gifted painters, such as
the Caracci, Gaspar Poussin, Claude Lorraine, and Ruysdael, to produce
the happiest and most varied creations of art, by their magical power
of managing the grouping of trees, and the effects of light and shade.
That progress which may still be expected in art, from a more animated
intercourse with the tropical world, and from ideas engendered in the
mind of the artist by the contemplation of Nature in her grandest
forms, will never diminish the fame of the old masters. I have alluded
to this, to recal the ancient bond which unites a knowledge of Nature
with poetry and a taste for art. For in landscape painting, as in
every other branch of art, a distinction must be drawn between the
elements generated by a limited field of contemplation and direct
observation, and those which spring from the boundless depth of
feeling, and from the force of idealising mental power. The grand
conceptions which landscape painting, as a more or less inspired
branch of the poetry of nature, owes to the creative power of the
mind, are, like man himself, and the imaginative faculties with which
he is endowed, independent of place. These remarks especially refer to
the gradations in the form of trees from Ruysdael and Everdingen,
through the works of Claude Lorraine, to Poussin and Annibal Caracci.
In the great masters of art there is no indication of local
limitation. But an extension of the visible horizon, and an
acquaintance with the nobler and grander forms of nature, and with the
luxuriant fulness of life in tropical regions, afford the advantage of
not simply enriching the material groundwork of landscape-painting,
but also of inducing more vivid impressions in the minds of less
highly gifted painters, and thus heightening their powers of artistic
creation.”

Footnote 105:

p. 230—“_From the thick and rough bark of the Crescentiæ and
Gustaviæ_.”

In _Crescentia Cujete_ (the Tutuma tree, whose large fruit-shells are
so indispensable to the natives as household utensils), in
_Cynometra_, the Cacao-tree (_Theobroma_), and the _Perigara Gustavia_
(Linn.), the tender blossoms burst forth from the half-carbonized
bark. When children eat the fruit of the _Pirigara speciosa_ (the
_Chupo_), their whole bodies become tinged with yellow; and this
jaundice, after a continuance of from twenty-four to thirty-six hours,
disappears without the use of medicine.

An indelible impression was produced on my mind by the luxuriant power
of vegetation in the tropical world, when, on entering a Cacao
plantation (_Caca hual_), in the Valles de Aragua, after a damp night,
I saw for the first time large blossoms springing from the root of a
_Theobroma_, deeply imbedded in the black soil. This is one of the
most instantaneous manifestations of the activity of the vegetative
force of organisation. Northern nations speak of “the awakening of
Nature at the first genial breath of Spring;”—expressions that
strongly contrast with the imaginative complaint of the Stagirite, who
regarded vegetable forms as buried in a “still sleep, from which there
is no awakening, and free from the desires that excite to spontaneous
motion.”[RB]

Footnote 106:

p. 230—“_Draw on their heads as caps_.”

These are the flowers of our _Aristolochia cordata_, to which
reference has been made in Illustration 25. The largest flowers in the
world, besides those belonging to the Compositæ (the Mexican
_Helianthus annuus_), are produced by _Rafflesia Arnoldi_,
_Aristolochia_, _Datura_, _Barringtonia_, _Gustavia_, _Carolinea_,
_Lecythis_, _Nymphæa_, _Nelumbium_, _Victoria Regina_, _Magnolia_,
_Cactus_, the Orchideæ, and the Liliaceous forms.

Footnote 107:

p. 231—“_The luminous worlds which spangle the firmament from pole to
pole_.”

The more magnificent portion of the southern sky, in which shine the
constellations of the Centaur, Argo, and the Southern Cross, where the
Magellanic clouds shed their pale light, is for ever concealed from
the eyes of the inhabitants of Europe. It is only under the equator
that man enjoys the glorious spectacle of _all_ the stars of the
southern and northern heavens revealed at one glance. Some of our
northern constellations,—as, for instance, Ursus Major and Ursus
Minor,—owing to their low position when seen from the region of the
equator, appear to be of a remarkable, almost fearful magnitude. As
the inhabitant of the tropics beholds _all_ stars, so too, in regions
where plains, deep valleys, and lofty mountains are alternated, does
Nature surround him with representatives of every form of vegetation.

* * * * *

In the foregoing sketch of a “Physiognomy of Plants,” I have
endeavoured to keep in view three nearly allied subjects,—_the
absolute diversity of forms_; their _numerical_ relations, _i.e._
their local preponderance in the whole number of phanerogamic floras;
and their _geographical and climatic distribution_. If we would rise
to a general view regarding vital forms;—the physiognomy, the study of
the numerical relations (the arithmetic of botany), and the geography
of plants (the study of the local zones of distribution), cannot, as
it seems to me, be separated from one another. The study of the
physiognomy of plants must not be exclusively directed to the
consideration of the striking contrasts of form which the larger
organisms present, when considered separately; but it must rise to the
recognition of the laws which determine _physiognomy of nature
generally_, the picturesque character of vegetation over the whole
surface of the earth, and the vivid impression produced by the
grouping of contrasted forms in different zones of latitude and
elevation. It is when concentrated into this focus that we first
clearly perceive the close and intimate connection existing between
the subjects treated of in the preceding pages. We have here entered
upon a field of inquiry hitherto but little cultivated. I have
ventured to follow the method first propounded with such brilliant
results in Aristotle’s zoological works, and which is so especially
adapted to establish scientific confidence,—a method in which the
incessant effort to arrive at a generalisation of ideas supported by
individual illustrations, is associated with an endeavour to penetrate
to the specialities of phenomena.

The enumeration of forms is, from the physiognomical difference of
their nature, incapable of any strict classification. Here, as
everywhere in the consideration of external forms, there are certain
main types which present the strongest contrasts,—as the groups of the
Arborescent Grasses, the Aloe form and the species of Cactus, Palms,
Acicular-leaved trees, Mimosaceæ, and Bananas. Even scantily dispersed
individuals belonging to these groups determine the character of a
district, and produce a lasting impression on the mind of the
unscientific but susceptible beholder. Other forms, perhaps more
numerous and preponderating, may not appear equally marked either by
the shape or position of the leaves; the relation of the stem to the
branches, luxuriant vigour, animation, and grace; or even by the
melancholy contraction of the leaf-organs.

As, therefore, a physiognomical classification, or a distribution into
groups according to external appearance, does not admit of being
applied to the whole vegetable kingdom collectively, the basis on
which such a classification should be grounded must necessarily be
wholly different from that which has been so happily chosen for the
establishment of our comprehensive systems of the natural families of
plants. Vegetable physiognomy grounds its divisions and the choice of
its types on all that possesses mass,—as the stem, branches, and
appendicular organs (the form, position, and size of the leaf, the
character and brilliancy of the parenchyma), and consequently on all
that is now included under the special term, _the organs of
vegetation_, and on which depend the preservation (nourishment and
development) of the individual; while systematic botany, on the other
hand, bases the arrangement of the natural families of plants on a
consideration of the organs of propagation, on which depends the
preservation of the species.[RC] It was already taught in the school
of Aristotle,[RD] that the generation of seed is the ultimate aim of
the being and life of a plant. The process of development in the
organs of fructification has become, since Caspar Fried. Wolf,[RE] and
our great poet Goëthe, the morphological basis of all systematic
botany.

This science and that also of vegetable physiognomy proceed, I would
here again observe, from two different points of view; the former
depending upon an accordance in the inflorescence and in the
reproduction of the delicate sexual organs; the latter on the
conformation of the parts constituting the axes (the stem and
branches) and on the outline of the leaves, which are mainly
determined by the distribution of the vascular bundles. As, moreover,
the stem and branches, together with their appendicular organs,
predominate by mass and volume, they determine and strengthen the
impression we receive, while they individualize the physiognomical
character of the vegetation, as well as that of the landscape or the
zone in which some distinguished types occur. The law is here
expressed by the accordance and affinity in the marks appertaining to
the vegetative, _i.e._ the nutritient organs. In all European colonies
the inhabitants have been led by resemblances of physiognomy
(_habitus_, _facies_) to apply the names of European forms to certain
tropical plants, which bear wholly different flowers and fruits from
the genera to which these designations originally referred. Everywhere
in both hemispheres, the northern settler has believed he could
recognise Alders, Poplars, Apple and Olive trees; being misled for the
most part by the form of the leaves and the direction of the branches.
The charm associated with the remembrance of native forms has
strengthened the illusion, and European names of plants have thus been
perpetuated from generation to generation in the slave colonies, where
they have been further enriched by denominations borrowed from the
negro languages.

A remarkable phenomenon is presented by the contrast frequently
observed to arise from a striking accordance in physiognomy, coupled
with the greatest difference in the organs of inflorescence and
fructification—between the external form as determined by the
appendicular or leaf-system, and the sexual organs on which are based
the various groups of the natural systems of botany. One would be
disposed _à priori_ to believe that the aspect of vegetative organs
(leaves) exclusively so called, must depend upon the structure of the
organs of reproduction, but this dependence has only been observed in
a very small number of families, as Ferns, Grasses, Cyperaceæ, Palms,
Coniferæ, Umbelliferæ, and Aroideæ. In the Leguminosæ this accordance
between the physiognomical character and the inflorescence can
scarcely be recognized, excepting where they are separated into groups
(as Papilionaceæ, Cæsalpinineæ, and Mimosaceæ.) The types which
exhibit, when compared together, a very different structure of
inflorescence and fructification, notwithstanding external accordance
in physiognomy, are Palms and Cycadeæ, the latter being most nearly
allied to the Coniferæ; _Cucusta_, belonging to the Convolvulaceæ, and
the leafless _Cassytha_, a parasitical Laurinea; _Equisetum_ (from the
division of the Cryptogamia) and _Ephedra_ (a coniferous tree). The
Grossulareæ (_Ribes_) are so nearly allied by their efflorescence to
Cactuses, _i. e._ the family of the Opuntiaceæ, that it is only very
lately that they have been separated from them! One common family
(that of the Asphodeleæ) comprises the gigantic tree, _Dracœna Draco_,
the Common Asparagus, and the coloured flowering _Aletris_. Simple and
compound leaves frequently belong not only to the same family, but
even to the same genus. We found in the elevated plateaux of Peru and
New Granada among twelve new species of _Weinmannia_, five with
simple, and the remainder with pinnate leaves. The genus _Aralia_
exhibits yet greater independence in the leaf-form, which is either
simple, entire, lobed, digitate, or pinnate.[RF]

Pinnate leaves appear to me to belong especially to those families
which occupy the highest grade of organic development, as for
instance, the _Polypetalœ_; among _perigynic_ plants, the Leguminosæ,
Rosaceæ, Terebinthaceæ, and Juglandeæ; among _hypogynic_ plants the
Aurantiaceæ, Cedrelaceæ, and Sapindaceæ. The elegant form of the
doubly pinnate leaf, which constitutes so great an adornment of the
torrid zone, is most frequently met with among the Leguminosæ; among
the Mimosaceæ, and also among some Cæsalpinias, Coulterias and
Gleditschias; but never, as Kunth has observed, among the
Papilionaceæ.

The form of pinnate, and more especially of compound leaves, is
unknown in Gentianeæ, Rubiaceæ, and Myrtaceæ. In the morphological
development presented by the richness and varied aspect of the
appendicular organs of dicotyledons, we are only able to recognize a
very small number of general laws.

ON THE
STRUCTURE AND MODE OF ACTION
OF
VOLCANOS
IN DIFFERENT PARTS OF THE EARTH.

(This Memoir was read at a Public Meeting of the Academy, at Berlin, on
the 24th January, 1823.)

When we consider the influence exerted on the study of nature during the last few centuries, by the extension of geographical knowledge and by means of scientific expeditions to remote regions of the earth, we are at once made sensible of the various character of this influence, according as the investigations have been directed to the forms of the organic world, the study of the inorganic crust of the earth, or to the knowledge of rocks, their relative ages, and their origin. Different vegetable and animal developments exist in every division of the earth, whether it be on the plains, where, on a level with the sea, the temperature varies with the latitude and with the various inflections of the isothermal lines, or on the steep declivity of mountain ranges, warmed by the direct rays of the sun. Organic nature imparts to every region of the globe its own characteristic physiognomy. But this does not apply to the inorganic crust of the earth divested of its vegetable covering, for everywhere, in both hemispheres, from the equator to the poles, the same rocks are found grouped with some relation to each other, either of attraction or repulsion. In distant lands, surrounded by strange forms of vegetation, and beneath a sky beaming with other stars than those to which his eye had been accustomed, the mariner often recognises, with joyful surprise, argillaceous schists and rocks familiar to him in his native land.

This independence of geological relations on the actual condition of climates does not diminish the beneficial influence exercised on the progress of mineralogy and physical geognosy by the numerous observations instituted in distant regions of the earth, but simply gives a particular direction to them. Every expedition enriches natural history with new genera of plants and animals. At one time we acquire a knowledge of new organic forms which are allied to types long familiar to us, and which not unfrequently, by furnishing links till then deficient, enable us to establish, in all its original perfection, an uninterrupted chain of natural structures. At another time we become acquainted with isolated structures, which appear either as the remains of extinct genera, or members of unknown groups, the discovery of which stimulates further research. It is not, however, from the investigation of the earth’s crust that we acquire these manifold additions to our knowledge, for here we meet rather with an uniformity in the constituent parts, in the superposition of dissimilar masses, and in their regular recurrence, which cannot fail to excite the surprise and admiration of the geologist. In the chain of the Andes, as in the mountains of Central Europe, one formation appears, as it were, to call forth another. Masses identical in character assume the same forms; basalt and dolerite compose twin mountains; dolomite, sandstone, and porphyry form abrupt rocky walls; while vitreous trachyte, containing a large proportion of feldspar, rises in bell-shaped and high-vaulted domes. In the most remote regions large crystals are separated in a similar manner from the compact texture of the fundamental mass, and, blending and grouping together into subordinate strata, frequently announce the commencement of new and independent formations. It is thus that the inorganic world may be said to reflect itself, more or less distinctly, in every mountain of any great extent. It is necessary, however, in order perfectly to understand the most important phenomena of the composition, relative age, and origin of formations, to compare together the observations made in regions of the earth most widely remote from each other. Problems which have long baffled the geologist in his own northern region, find their solution in the vicinity of the equator. If, as we have already observed, remote regions do not present us with new formations, that is to say, with unknown groupings of simple substances, they at least help us to unravel the great and universal laws of nature, by showing how different strata of the crust of the earth are mutually superimposed on, and intersect, each other in the form of veins, or rise to different elevations in obedience to elastic forces.

Although our geological knowledge may be thus extensively augmented by researches over vast regions, it can hardly be a matter of surprise that the class of phenomena constituting the principal subject of this address should have been so long examined in an imperfect manner, since the means of comparison were of difficult, and almost, it may be said, of laborious access.