known intertropical species, so far as I am aware. We collected seven
new species, three of which were from the elevated plains of Mexico,
and were found to extend to an elevation of 8000 (about 8500 English)
feet above the level of the sea. At still greater elevations,--for
example, on the mountain plains situated between 12000 and 14000
feet, (about 12790 and 14920 English,) which we often visited,--we
did not find, either in the Andes of Mexico or in those of Quito and
Peru, anything which could recall the small creeping alpine willows of
the Pyrenees, the Alps, and Lapland (S. herbacea, S. lanata, and S.
reticulata). In Spitzbergen, where the meteorological conditions have
much analogy with those of the Swiss and Scandinavian snow-mountains,
Martins described two dwarf willows, of which the small woody stems
and branches creep on the ground, and which lie so concealed in the
turf-bogs that their small leaves are only discovered with difficulty
under the moss. The species found by me in Peru in 4° 12´ S. latitude,
near Loxa, at the entrance of the forests where the best Cinchona
bark is collected, and described by Willdenow as Salix humboldtiana,
is the one which is most widely distributed in the western part of
South America. A sea-shore species, S. falcata, which we found on the
sandy coast of the Pacific, near Truxillo, is, according to Kunth,
probably only a variety of the above; and possibly the fine and often
pyramidal willow which accompanied us along the banks of the Magdalena,
from Mahates to Bojorque, and which, according to the report of the
natives, had only extended so far within a few years, may also be
identical with Salix humboldtiana. At the confluence of the Rio Opon
with the Magdalena, we found all the islands covered with willows, many
of which had stems 64 English feet high, but only 8 to 10 inches in
diameter. (Humboldt and Kunth, Nova Gen. Plant. T. ii. p. 22, tab. 99.)
Lindley has made us acquainted with a species of Salix from Senegal,
and therefore in the African equinoctial zone. (Lindley, Introduction
to the Natural System of Botany, p. 99.) Blume also found two species
of Salix near the equator, in Java: one wild and indigenous, S.
tetrasperma; and another cultivated, S. sieboldiana. From the southern
temperate zone I know only two willows described by Thunberg, (S.
hirsuta and S. mucronata); they grow by the side of Protea argentea
(which has itself very much the physiognomy of a willow), on the banks
of the Orange River, and their leaves and young shoots form the food
of the hippopotamus. Willows are entirely wanting in Australia and the
neighbouring islands.
[31] p. 29.--“_Myrtaceæ._”
An elegant form, with stiff, shining, thickly set, generally
unindented, small leaves, studded with pellucid dots. Myrtaceæ give
a peculiar character to three districts of the earth’s surface,--the
South of Europe, particularly the calcareous and trachytic islands
which rise above the surface of the Mediterranean;--the continent
of New Holland, adorned with Eucalyptus, Metrosideros, and
Leptospermum;--and an intertropical region, part of which is low, and
part from nine to ten thousand feet high (about 9590 to 10660 English),
in the Andes of South America. This mountain district, called in Quito
the district of the Paramos, is entirely covered with trees which have
a myrtle-like aspect and character, even though they may not all belong
to the natural family of Myrtaceæ. Here, at the above-named elevation,
grow the Escallonia myrtilloides, E. tubar, Simplocos alstonia, some
species of Myrica, and the beautiful Myrtus microphylla which we have
figured in the Plantes équinoxiales, T. i. p. 21, Pl. iv. We found it
growing on mica slate, and extending to an elevation of more than ten
thousand English feet, on the Paramo de Saraguru, near Vinayacu and
Alto de Pulla, which is adorned with so many lovely alpine flowering
plants. Myrtus myrsinoides even extends in the Paramo de Guamani up
to 10500 (11190 English) feet. Of the 40 species of the Genus Myrtus
which we collected in the equinoctial zone, and of which 37 were
undescribed, much the greater part belonged, however, to the plains and
lower mountains. From the mild tropical mountain climate of Mexico we
brought back only a single species (Myrtus xalapensis); but the Tierra
templada, towards the Volcano of Orizaba, must no doubt contain several
more. We found M. maritima near Acapulco, quite on the sea-coast of the
Pacific.
The Escallonias,--among which E. myrtilloides, E. tubar, and E.
floribunda, are the ornament of the Paramos, and by their physiognomy
remind the beholder strongly of the myrtle-form,--once constituted,
in combination with the European and South American Alp-roses
(Rhododendrum and Befaria), and with Clethra, Andromeda, and
Gaylussaccia buxifolia, the family of Ericeæ. Robert Brown (see the
Appendix to Franklin’s Narrative of a Journey to the Shores of the
Polar Sea, 1823, p. 765), has raised them to the rank of a separate
family, which Kunth places between Philadelpheæ and Hamamelideæ. The
Escallonia floribunda offers in its geographical distribution one of
the most striking examples, in the habitat of the plant, of proportion
between distance from the equator and vertical elevation above the
level of the sea. In making this statement I again support myself on
the authority of my acute and judicious friend Auguste de St.-Hilaire
(Morphologie végétale, 1840, p. 52):--“Messieurs de Humboldt et
Bonpland ont découvert dans leur expédition l’Escallonia floribunda à
1400 toises par les 4° de latitude australe. Je l’ai retrouvé par les
21° au Brésil dans un pays élevé, mais pourtant infiniment plus bas que
les Andes du Pérou: il est commun entre les 24°.50´ et les 25°.55´ dans
les Campos Geræs, enfin je le revois au Rio de la Plata vers les 35°,
au niveau même l’ocean.”
Trees belonging the group of Myrtaceæ,--to which Melaleuca,
Metrosideros, and Eucalyptus belong in the sub-division of
Leptospermeæ,--produce partially, either where the leaves are replaced
by phyllodias (leaf-stalk leaves), or by the peculiar disposition or
direction of the leaves relatively to the unswollen leaf-stalk, a
distribution of stripes of light and shade unknown in our forests of
round-leaved trees. The first botanical travellers who visited New
Holland were struck with the singularity of the effect thus produced.
Robert Brown was the first to show that this strange appearance arose
from the leaf-stalks (the phyllodias of the Acacia longifolia and
A. suaveolens) being expanded in a vertical direction, and from the
circumstance that the light instead of falling on horizontal surfaces,
falls on and passes between vertical ones. (Adrien de Jussieu, Cours
de Botanique, p. 106, 120, and 700; Darwin, Journal of Researches,
1845, p. 433). Morphological laws in the development of the leafy
organs determine the peculiar character of the effects produced, the
outlines of light and shade. “Phyllodias,” says Kunth, “can, according
to my view, only occur in families which have compound pinnated leaves;
and in point of fact they have as yet only been found in Leguminosæ,
(in Acacias). In Eucalyptus, Metrosideros, and Melaleuca, the leaves
are simple (simplicia), and their edgewise position arises from a half
turn or twist of the leaf-stalk (petiolus); it should be remarked at
the same time that the two surfaces of the leaves are similar.” In the
comparatively shadeless forests of New Holland the optical effects
here alluded to are the more frequent, as two groups of Myrtaceæ and
Leguminosæ, species of Eucalyptus and of Acacia, constitute almost the
half of all the greyish green trees of which those forests consist.
In addition to this, in Melaleuca there are formed between the layers
of the inner bark easily detached portions of epidermis which press
outwards, and by their whiteness remind the European of our birch bark.
The distribution of Myrtaceæ is very different in the two continents.
In the New Continent, and especially in its western portion, it
scarcely extends beyond the 26th parallel of north latitude, according
to Joseph Hooker (Flora antarctica, p. 12); while in the Southern
Hemisphere, according to Claude Gay, there are in Chili 10 species of
Myrtus and 22 species of Eugenia, which, intermixed with Proteaceæ
(Embothrium and Lomatia), and with Fagus obliqua, form forests. The
Myrtaceæ become more abundant beyond 38° S. lat.,--in the Island of
Chiloe, where a Metrosideros-like species of Myrtus (Myrtus stipularis)
forms almost impenetrable thickets under the name of Tepuales; in
Patagonia; and in Fuegia to its extremity in 56-1/2° S. lat. In the
Old Continent they prevail in Europe as far as the 46th parallel of
North latitude: in Australia, Tasmania, New Zealand, and the Auckland
Islands, they advance to 50-1/2° South latitude.
[32] p. 29.--“_Melastomaceæ._”
This group comprises the genera Melastoma (Fothergilla and Tococa
Aubl.) and Rhexia (Meriana and Osbeckia), of which we found, on either
side of the equator in tropical America alone, 60 new species. Bonpland
has published a superb work on Melastomaceæ, in two volumes, with
coloured drawings. Some species of Rhexia and Melastoma ascend in the
Andes, as alpine or Paramos shrubs, as high as nine and ten thousand
five hundred (about 9600 and 11190 English) feet: among these are
Rhexia cernua, R. stricta, Melastoma obscurum, M. aspergillare, and M.
lutescens.
[33] p. 29.--“_Laurel-form._”
To this form belong the genera of Laurus and Persea, the Ocoteæ
so numerous in South America, and (on account of physiognomic
resemblance), Calophyllum and the superb aspiring Mammea, from among
the Guttiferæ.
[34] p. 29.--“_How interesting and instructive to the landscape painter
would be a work which should present to the eye the leading forms of
vegetation!_”
In order to define somewhat more distinctly what is here only briefly
alluded to, I permit myself to introduce some considerations taken
from a sketch of the history of landscape painting, and of a graphical
representation of the physiognomy of plants, which I have given in the
second volume of Kosmos (Bd. ii. S. 88-90; English edit. vol. ii. p.
86-87).
“All that belongs to the expression of human emotion and to the beauty
of the human form, has attained perhaps its highest perfection in the
northern temperate zone, under the skies of Italy and Greece. By the
combined exercise of imitative art and of creative imagination, the
artist has derived the types of historical painting at once from the
depths of his own mind, and from the contemplation of other beings
of his own race. Landscape painting, though no merely imitative art,
has, it may be said, a more material substratum and a more terrestrial
domain: it requires a greater mass and variety of distinct impressions,
which the mind must receive within itself, fertilize by its own powers,
and reproduce visibly as a free work of art. Hence landscape painting
must be a result at once of a deep and comprehensive reception of the
visible spectacle of external nature, and of this inward process of the
mind.”
“Nature, in every region of the earth, is indeed a reflex of the
whole; the forms of organised beings are repeated everywhere in
fresh combinations; even in the icy north, herbs covering the earth,
large alpine blossoms, and a serene azure sky, cheer a portion of the
year. Hitherto landscape painting has pursued amongst us her pleasing
task, familiar only with the simpler form of our native floras, but
not, therefore, without depth of feeling, or without the treasures
of creative imagination. Even in this narrower field, highly gifted
painters, the Caracci, Gaspar Poussin, Claude Lorraine, and Ruysdael,
have with magic power, by the selection of forms of trees and by
effects of light, found scope wherein to call forth some of the most
varied and beautiful productions of creative art. The fame of these
master-works can never be impaired by those which I venture to hope
for hereafter, and to which I could not but point, in order to recall
the ancient but deeply-seated bond which unites natural knowledge
with poetry and with artistic feeling; for we must ever distinguish
in landscape painting, as in every other branch of art, between
productions derived from direct observation, and those which spring
from the depths of inward feeling and from the power of the idealising
mind. The great and beautiful works which owe their origin to this
creative power of the mind applied to landscape-painting, belong to
the poetry of nature, and like man himself, and the imagination with
which he is gifted, are not rivetted to the soil, or confined to any
single region. I allude here more particularly to the gradation in the
form of trees from Ruysdael and Everdingen, through Claude Lorraine
to Poussin and Annibal Caracci. In the great masters of the art we
perceive no trace of local limitation; but an enlargement of the
visible horizon, and an increased acquaintance with the nobler and
grander forms of nature, and with the luxuriant fulness of life in the
tropical world, offer the advantage not only of enriching the material
substratum of landscape painting, but also of affording a more lively
stimulus to less gifted artists, and of thus heightening their powers
of production.”
[35] p. 30.--“_From the rough bark of Crescentias and Gustavia._”
In the Crescentia cujete (the Tutuma or Calabash-tree, whose large
fruit-shells are so useful to the natives for household purposes),--in
the Cynometra, the Theobroma (the Cacao-tree), and the Perigara (the
Gustavia of Linnæus),--the delicate flowers break through the half
carbonized bark. When children eat the fruit of the Pirigara speciosa
(the Chupo), their whole body becomes tinged with yellow; it is a
jaundice, which lasts from 24 to 36 hours, and then disappears without
the use of medicine.
I have never forgotten the impression which I received of 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 a root of the
Theobroma deeply imbedded in black earth. It was one of the most
instantaneous manifestations of the activity of the vegetative organic
forces. Northern nations speak of the “awakening of Nature at the first
breath of the mild air of spring.” Such an expression is singularly
contrasted with the imagination of the Stagirite, who recognised in
plants forms which “lie buried in a tranquil slumber that knows no
waking, free from the desires which impel to spontaneous motion.”
(Aristot. de generat. Animal. V. i. p. 778, and de somno et vigil. cap.
1, p. 455, Bekker.)
[36] p. 30.--“_Draw over their heads._”
The flowers of our Aristolochia cordata, to which I have already
referred in Note 25. The largest flowers in the world, apart from
Compositæ (in the Mexican Helianthus annuus), belong to Rafflesia
arnoldi, Aristolochia, Datura, Barringtonia, Gustavia, Carolinea,
Lecythis, Nymphæa, Nelumbium, Victoria regina, Magnolia, Cactus, and to
Orchideous and Liliaceous plants.
[37] p. 31--“_To behold all the shining worlds which stud the heavenly
vault from pole to pole._”
The finest portion of the southern celestial hemisphere, where shine
the constellations of the Centaur, the Ship, and the southern Cross,
and where the soft lustre of the Magellanic clouds is seen, remains for
ever concealed from the view of the inhabitants of Europe. It is only
beneath the equinoctial line that Man enjoys the peculiar privilege of
beholding at once all the stars both of the Southern and the Northern
heavens. Some of our northern constellations seen from thence appear
from their low altitude of a surprising and almost awful magnitude:
for example, Ursus major and minor. As the inhabitant of the tropics
sees all the stars of the firmament, so also, in regions where plains
alternate with deep valleys and lofty mountains, Nature surrounds him
with representatives of all the forms of plants.
POSTSCRIPT
ON THE
PHYSIOGNOMIC CLASSIFICATION OF PLANTS.
In the preceding sketch of a “Physiognomy of Plants,” I have had
principally in view three nearly allied subjects:--the absolute
diversity of forms; their numerical proportion, _i. e._ their local
predominance in the total number of species in phænogamous floras;
and their geographic and climatic distribution. If we desire to
rise to general views respecting organic forms, the physiognomy of
plants, the study of their numerical proportions (or the arithmetic
of botany),--and their geography (or the study of their zones of
distribution),--cannot, as it appears to me, be separated from each
other. In the study of the physiognomy of plants, we ought not to
dwell exclusively on the striking contrasts presented by the larger
organic forms separately considered, but we should also seek to discern
the laws which determine the physiognomy of Nature generally, or the
picturesque character of vegetation over the entire surface of the
globe, and the impression produced on the mind of the beholder by the
grouping of contrasted forms in different zones of latitude and of
elevation. It is from this point of view, and with this concentration
or combination of objects, that we become aware, for the first time,
of the close and intimate connection between the subjects which have
been treated of in the foregoing pages. We are here conducted into a
field which has been as yet but little cultivated. I have ventured to
follow the method first employed with such brilliant results in the
Zoological works of Aristotle, and which is especially suited to lay
the foundation of scientific confidence,--a method which, whilst it
continually aims at generality of conception, seeks, at the same time,
to penetrate the specialities of phenomena by the consideration of
particular instances.
The enumeration of forms according to physiognomic diversity is, from
the nature of the case, not susceptible of any strict classification.
Here, as everywhere else, in the consideration of external
conformation, there are certain leading forms which present the most
striking contrasts: such are the groups of arborescent grasses, plants
of the aloë form, the different species of cactus, palms, needle-trees,
Mimosaceæ, and Musaceæ. Even a few scattered individuals of these
groups are sufficient to determine the character of a district, and
to produce on a non-scientific but sensitive beholder a permanent
impression. Other forms, though perhaps much more numerous and
preponderating in mass, may not be calculated either by the outline
and arrangement of the foliage, or by the relation of the stem to the
branches,--by luxuriant vigour of vegetation,--by cheerful grace,--or,
on the other hand, by cheerless contraction of the appendicular organs,
to produce any such characteristic impressions.
As, therefore, a “physiognomic classification,” or a division
into groups from external aspect or “facies,” does not admit of
being applied to the whole vegetable kingdom, so also, in such a
classification, the grounds on which the division is made are quite
different from those on which our systems of natural families and of
plants (including the whole of the vegetable kingdom) have been so
happily established. Physiognomic classification grounds her divisions
and the choice of her types on whatever possesses “mass,”--such
as shape, position and arrangement of leaves, their size, and the
character and surfaces (shining or dull) of the parenchyma,--therefore,
on all that are called more especially the “organs of vegetation,”
_i. e._ those on which the preservation,--the nourishment and
development,--of the individual depend; while systematic Botany,
on the other hand, grounds the arrangement of natural families on
the consideration of the organs of propagation,--those on which the
continuation or preservation of the species depends. (Kunth, Lehrbuch
der Botanik, 1847, Th. i. S. 511; Schleiden, die Pflanze und ihr
Leben, 1848, S. 100). It was already taught in the school of Aristotle
(Probl. 20, 7), that the production of seed is the ultimate object
of the existence and life of the plant. Since Caspar Fried. Wolf
(Theoria Generationis, § 5-9), and since our great (German) Poet, the
process of development in the organs of fructification has become the
morphological foundation of all systematic botany.
That study, and the study of the physiognomy of plants, I here repeat,
proceed from two different points of view: the first from agreement
in the inflorescence or in the delicate organs of reproduction; the
second from the form of the parts which constitute the axes (_i.
e._ the stems and branches), and the shape of the leaves, dependent
principally on the distribution of the vascular fascicles. As, then,
the axes and appendicular organs predominate by their volume and
mass, they determine and strengthen the impression which we receive;
they individualise the physiognomic character of the vegetable form
and that of the landscape, or of the region in which any of the more
strongly-marked and distinguished types severally occur. The law is
here given by agreement and affinity in the marks taken from the
vegetative, _i. e._ the nutritive organs. In all European colonies,
the inhabitants have taken occasion, from resemblances of physiognomy
(of “habitus,” “facies”), to bestow the names of European forms upon
tropical plants or trees bearing very different flowers and fruits
from those from which the names were originally taken. Everywhere, in
both hemispheres, northern settlers have thought they found Alders,
Poplars, Apple- and Olive-trees. They have been misled in most cases by
the form of the leaves and the direction of the branches. The illusion
has been favoured by the cherished remembrance of the trees and plants
of home, and thus European names have been handed down from generation
to generation; and in the slave colonies there have been added to them
denominations derived from Negro languages.
The contrast so often presented between a striking agreement of
physiognomy and the greatest diversity in the inflorescence and
fructification,--between the external aspect as determined by the
appendicular or leaf-system, and the reproductive organs on which the
groups of the natural systems of botany are founded,--is a remarkable
and surprising phenomenon. We should have been inclined beforehand to
imagine that the shape of what are exclusively termed the vegetative
organs (for example, the leaves) would have been less _independent_
of the structure of the organs of reproduction; but in reality such a
dependence only shows itself in a small number of families,--in Ferns,
Grasses and Cyperaceæ, Palms, Coniferæ, Umbelliferæ, and Aroideæ. In
Leguminosæ the agreement in physiognomic character is scarcely to be
recognised until we divide them into the several groups (Papilionaceæ,
Cæsalpinineæ, and Mimoseæ). I may name, of types which, when compared
with each other, shew considerable accordance in physiognomy with
great difference in the structure of the flowers and fruit, Palms and
Cycadeæ, the latter being more nearly allied to Coniferæ; Cuscuta,
one of the Convolvulacæ, and the leafless Cassytha, a parasitical
Laurinea; Equisetum (belonging to the great division of Cryptogamia),
and Ephedra, closely allied to Coniferæ. On the other hand, our common
gooseberries and currants (Ribes) are so closely allied by their
inflorescence to the Cactus, _i. e._ to the family of Opuntiaceæ, that
it is only quite recently that they have been separated from it! One
and the same family (that of Asphodeleæ) comprises the gigantic Dracæna
draco, the common asparagus, and the Aletris with its coloured flowers.
Not only do simple and compound leaves often belong to the same family,
but they even occur in the same genus. We found in the high plains of
Peru and New Granada, among twelve new species of Weinmannia, five
with “foliis simplicibus,” and the rest with pinnate leaves. The genus
Aralia shews still greater independence in the form of the leaves:
“folia simplicia, integra, vel lobata, digitata et pinnata.” (Compare
Kunth, Synopsis Plantarum quas in itinere collegerunt, Al. de Humboldt
et Am. Bonpland, T. iii, p. 87 and 360.)