physiognomy, belong; Yucca aloifolia, which extends as far north as
Florida and South Carolina; Y. angustifolia (Nutt.) which advances as
far as the banks of the Missouri; Aletris arborea; the Dragon-tree
of the Canaries and two other Dræcænas from New Zealand; arborescent
Euphorbias; Aloë dichotoma (Linn.) (formerly the genus Rhipidodendrum
of Willdenow); and the celebrated Koker-boom of Southern Africa with a
trunk twenty-one feet high and above four feet thick, and a top of 400
(426 Engl.) feet in circumference. (Patterson, Reisen in das Land der
Hottentotten und der Kaffern, 1790, S. 55.) The forms which I have thus
brought together belong to very different families: to the Liliaceæ,
Asphodeleæ, Pandaneæ, Amaryllideæ, and Euphorbiaceæ; all, however,
with the exception of the last, belonging to the great division of
the Monocotyledones. A Pandanea, Phytelephas macrocarpa (Ruiz,) which
we found in New Granada on the banks of the Magdalena, with its
pinnated leaves, quite resembles in appearance a small palm-tree. This
Phytelephas, of which the Indian name is Tagua, is besides, as Kunth
remarks, the only one of the Pandaneæ found (according to our present
knowledge) in the New Continent. The singular Agave-like and at the
same time very tall-stemmed Doryanthes excelsa of New South Wales,
which was first described by the acutely observing Correa de Serra, is
an Amaryllidea, like our low-growing Narcissuses and Jonquils.
In the Candelabra shape of plants of the Aloë form, we must not
confound the branches of an arborescent stem with flower-stalks. It
is the latter which in the American Aloë (Agave Americana, Maguey
de Cocuyza, which is entirely wanting in Chili) as well as in the
Yucca acaulis, (Maguey de Cocuy) presents in the rapid and gigantic
development of the inflorescence a candelabrum-like arrangement of the
flowers which, as is well known, is but too transient a phenomenon.
In some arborescent Euphorbias, on the other hand, the physiognomic
effect is given by the branches and their division, or by ramification
properly so called. Lichtenstein, in his “Reisen im südlichen Africa”
(Th. i. S. 370), gives a vivid description of the impression made upon
him by the appearance of a Euphorbia officinarum which he found in the
“Chamtoos Rivier,” in the Colony of the Cape of Good Hope; the form of
the tree was so symmetrical that the candelabrum-like arrangement was
regularly repeated on a smaller scale in each of the subdivisions of
the larger branches up to 32 English feet high. All the branches were
armed with sharp spines.
Palms, Yuccas, Aloes, tall-stemmed Ferns, some Aralias, and the
Theophrasta where I have seen it growing luxuriantly, different as they
are in the structure of their flowers, yet offer to the eye in the
nakedness (absence of branches) of their stems, and in the ornamental
character of their tops or crowns, a certain degree of physiognomic
resemblance.
The Melanoselinum decipiens (Hofm.), which is sometimes upwards
of 10 or 12 feet high, and which has been introduced into our
gardens from Madeira, belongs to a peculiar group of arborescent
umbelliferous plants to which Araliaceæ are otherwise allied, and
with which other plants which will doubtless be discovered in course
of time will be associated. Ferula, Heracleum, and Thapsia, do indeed
attain a considerable height, but they are still herbaceous plants.
Melanoselinum is still almost entirely alone as an umbelliferous
tree; Bupleurum (Tenonia) fruticosum (Linn.) of the shores of the
Mediterranean; Bubon galbanum of the Cape, and Crithmum maritimum
of our sea-shores, are only shrubs. On the other hand, the tropical
zone, in which, according to the old and very just remark of Adanson,
Umbelliferæ and Cruciferæ are almost entirely wanting in the plains,
presented to us on the high ridges of the American Andes the smallest
and most dwarf-like of all umbelliferous plants. Among 38 species of
plants which we collected at elevations where the mean temperature is
below 10° Reaumur (54°.5 Fah.), there vegetate almost like mosses, and
as if they made part of the rock and of the often frozen earth, at an
elevation of 12600 (13430 English) feet above the level of the sea,
Myrrhis andicola, Fragosa arctioïdes, and Pectophytum pedunculare,
intermingled with which there is an equally dwarfed Alpine Draba. The
only umbelliferous plants growing in the low grounds within the tropics
observed by us in the New Continent were two species of Hydrocotyle (H.
umbellata and H. leptostachya) between Havannah and Batabano; therefore
at the extreme limits of the torrid Zone.
[27] p. 27--“_The form of Gramineæ._”
The group of arborescent grasses which Kunth, in his able treatise
on the plants collected by Bonpland and myself, has combined under
the name of Bambusaceæ, is among the most beautiful adornments of
the tropical world. (Bambu, also called Mambu, is a word in the
Malay language, but appears according to Buschmann to be of doubtful
origin, as the usual Malay expression is buluh, in Java and Madagascar
wuluh, voulu.) The number of genera and species which form this
group has been extraordinarily augmented by the zeal of botanists.
It is now recognised that the genus Bambusa is entirely wanting in
the New Continent, to which on the other hand Guadua, from 50 to 60
French or about 53 to 64 English feet high, discovered by us, and
Chusquea, exclusively belong; that Arundinaria (Rich) is common to
both continents, although the species are different; that Bambusa and
Beesha (Rheed.) are found in India and the Indian Archipelago, and
Nastus in the Island of Bourbon, and in Madagascar. With the exception
of the tall-climbing Chusquea the forms which have been named may be
said to replace each other morphologically in the different parts of
the world. In the northern hemisphere, in the valley of the Mississipi,
the traveller is gratified, long before reaching the tropics, with
the sight of a form of bamboo, the Arundinaria macrosperma, formerly
called also Miegia, and Ludolfia. In the Southern Hemisphere Gay has
discovered a Bambusacea, (a still undescribed species of Chusquea,
21 English feet high, which does not climb, but is arborescent and
self-supporting) growing in southern Chili between the parallels of 37°
and 42° S. latitude; where, intermixed with Drymis chilensis, a uniform
forest covering of Fagus obliqua prevails.
While in India the Bambusa flowers so abundantly that in Mysore and
Orissa the seeds are mixed with honey and eaten like rice, (Buchanan,
Journey through Mysore, Vol. ii. p. 341, and Stirling in the Asiat.
Res. Vol. xv, p. 205) in South America the Guadua flowers so rarely,
that in four years we were only twice able to procure blossoms; once
on the unfrequented banks of the Cassiquiare, (the arm which connects
the Orinoco with the Rio Negro and the Amazons River,) and once in the
province of Popayan between Buga and Quilichao. It is striking to see
plants in particular localities grow with the greatest vigour without
producing flowers: it is thus with European olive trees which have
been planted for centuries between the tropics near Quito, 9000 (about
9590 English) feet above the level of the sea, and also in the Isle of
France with Walnut-trees, Hazel-nuts, and, as at Quito, olive trees
(Olea europea): see Bojer, Hortus Mauritianus, 1837, p. 291.
As some of the Bambusaceæ (arborescent grasses) advance into the
temperate zone, so within the tropics they do not suffer from
the temperate climate of the mountains. They certainly grow more
luxuriantly as social plants from the sea coast to the height of about
2560 English feet; for example, in the province de las Esmeraldas, west
of the Volcano of Pichincha, where Guadua angustifolia (Bambusa Guadua
in our Plantes équinoxiales, T. i. Tab. xx.) produces in its interior
much of the siliceous Tabaschir (Sanscrit _tvakkschira_, ox-milk). In
the pass of Quindiu we saw the Guadua growing at an elevation which we
found by barometric measurement to be 5400 (5755 English) feet above
the level of the Pacific. Nastus borbonicus is called by Bory de St.
Vincent a true Alpine plant; he states that it does not descend lower
on the declivity of the Volcano in the Island of Bourbon than 3600
(3837 English) feet. This recurrence or repetition as it were at great
elevations of the forms characteristic of the hot plains, recalls the
mountain group of palms before pointed out by me (Kunthia Montana,
Ceroxylon andicola, and Oreodoxa frigida), and a grove or thicket of
Musaceæ sixteen English feet high (Heliconia, perhaps Maranta), which I
found growing isolated at an elevation of 6600 (7034 English) feet, on
the Silla de Caraccas. (Rélation hist. T. i. p. 605-606.) As, with the
exception of a few isolated herbaceous dicotyledones, grasses form the
highest zone of phænogamous vegetation round the snowy summits of lofty
mountains, so also, in advancing in a horizontal direction towards
either pole of the Earth, the phænogamous vegetation terminates with
grasses.
To my young friend Joseph Hooker, who, but just returned with Sir
James Ross from the frozen antarctic regions, is now exploring the
Thibetian portion of the Himalaya, the geography of plants is indebted
not only for a great mass of important materials, but also for
excellent general deductions. He calls attention to the circumstance
that phænogamous flowering plants (grasses) approach 17-1/2° nearer
to the Northern than to the Southern pole. In the Falkland Islands
near the thick masses of Tussack grass (Dactylis cæspitosa, Forster,
according to Kunth a Festuca), and in Tierra del Fuego or Fuegia,
under the shade of the birch-leaved Fagus antarctica, there grows the
same Trisetum subspicatum which extends over the whole range of the
Peruvian Cordilleras, and over the Rocky Mountains to Melville Island,
Greenland, and Iceland, and which is also found in the Swiss and
Tyrolese Alps, in the Altai mountains, in Kamtschatka, and in Campbell
Island, south of New Zealand; therefore, from 54° South to 74-1/2°
North latitude, or through 128-1/2° of latitude. “Few grasses,” says
Joseph Hooker, in his Flora Antarctica, p. 97, “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 divided by Bransfield
Strait from D’Urville’s Terre de Louis Philippe and the Volcano of
Haddington Peak, situated in 64° 12´ South latitude and 7046 English
feet high, have been very recently visited by a Botanist from the
United States of North America, Dr. Eights. He found there (probably in
62° or 62-1/4°, S. latitude) a small grass, Aira antarctica (Hooker,
Icon. Plant. Vol. ii. Tab. 150) which is “the most antarctic flowering
plant hitherto discovered.”
In Deception Island, of the same group, S. lat. 62° 50´, lichens only
are found, and not a single species of grass; and so also farther to
the south-east, in Cockburn Island (lat. 64° 12´), near Palmer’s Land,
there were only found Lecanoras, Lecideas, and five Mosses, among which
was our German Bryum argenteum: “this seems to be the ultima Thule of
antarctic vegetation.” Farther to the south, _land_-cryptogamic, as
well as phænogamic, vegetation is entirely wanting. In the great bay
formed by Victoria Land, on a small island which lies opposite to Mount
Herschel (S. lat. 71° 49´), and in Franklin Island, 92 geographical
miles North of the great volcano Mount Erebus, 12400 English feet high
(latitude 76° 7´ South), Hooker found not a single trace of vegetable
life. It is quite different in respect to the extension even of the
forms of higher vegetable organisation in the high northern latitudes.
Phænogamous plants there approach 18-1/2° nearer to the pole than in
the southern hemisphere: Walden Island (N. lat. 80-1/2°) has still
ten species. The antarctic phænogamous vegetation is also poorer in
species at corresponding distances from the pole (Iceland has five
times as many flowering plants as the southern group of Auckland and
Campbell Islands), but this less varied antarctic vegetation is from
climatic reasons more luxuriant and succulent. (Compare Hooker, Flora
antarctica, p. vii., 74, and 215, with Sir James Ross, Voyage in the
Southern and Antarctic Regions, 1839-1843, Vol. ii. p. 335-342.)
[28] p. 28.--“_Ferns._”
If, with a naturalist deeply versed in the knowledge of the Agamæ,
Dr. Klotzsch, we estimate the whole number of cryptogamic species
hitherto described at 19000, this gives to Fungi 8000 (of which the
Agarici constitute 1-8th); Lichens, according to J. von Flotow of
Hirschberg, and Hampe of Blankenburg, at least 1400; Algæ 2580; Mosses
and Liver-worts, according to Carl Müller of Halle, and Dr. Gottsche
of Hamburgh, 3800; and Ferns 3250. We are indebted for this last
important result to the thorough investigation of all that is known
concerning this group of plants by Professor Kunze of Leipsic. It is
remarkable that of the entire number of described Filices the family of
Polypodiaceæ, alone, comprises 2165 species; while other forms, even
Lycopodiaceæ and Hymenophyllaceæ, only count 350 and 200. There are,
therefore, almost as many described ferns as described grasses.
It is remarkable that in the ancient classic writers, Theophrastus,
Dioscorides, and Pliny, no notice occurs of the beautiful form of
arborescent ferns; while from information derived from the companions
of Alexander, Aristobulus, Megasthenes, and Nearchus, mention is made
of Bamboos “quæ fissis internodiis lembi vice vectitabant navigantes;”
of the Indian trees “quarum folia non minora clypeo sunt;” of the
fig-tree of which the branches take root round the parent stem; and of
Palms “tantæ proceritatis, ut sagittis superjici nequeant.” (Humboldt,
de Distributione geogr. Plantarum, p. 178 and 213.) I find the first
description of tree-ferns in Oviedo’s Historia de las Indias, 1535,
fol. xc. This experienced traveller, who had been placed by Ferdinand
the Catholic as director of the gold-washings in Hayti, says: “Among
the many ferns there are some which I reckon among trees, for they are
as thick and as tall as pines (Helechos que yo cuento por arboles,
tan gruesos como grandes pinos y muy altos). They grow chiefly in the
mountains and where there is much water.” The height is exaggerated.
In the dense forests round Caripe even our Cyathea speciosa only
attains a height of 30 to 35 (32 to 37 English) feet; and an excellent
observer, Ernst Dieffenbach, in the northernmost of the three islands
of New Zealand saw no stems of Cyathea dealbata of more than 40 (42-1/2
English) feet in height. In the Cyathea speciosa and the Meniscium of
the Chaymas missions we observed, in the midst of the shadiest primeval
forest, in very luxuriantly growing individuals, the scaly stems
covered with a shining carbonaceous powder. It seemed like a singular
decomposition of the fibrous parts of the old frond stalks. (Humboldt,
Rel. hist. T. i. p. 437.)
Between the tropics, where, on the declivities of the Cordilleras,
climates are placed successively in stages one above another, the
proper zone of the tree-ferns is between three and five thousand feet
(about 3200 and 5330 English) above the level of the sea. In South
America and in the Mexican highlands they seldom descend lower towards
the plains than 1200 (about 1280 Eng.) feet. The mean temperature
of this happy zone falls between 17° and 14°.5 Reaumur (70°.2 and
64°.6 Fahr.) This region enters the lowest stratum of clouds, or
that which floats next above the sea and the plains; and hence,
besides great equality of temperature, it also enjoys uninterruptedly
a high degree of humidity. (Robert Brown, in Appendix to Expedition
to Congo, p. 423.) The inhabitants, who are of Spanish descent, call
this zone “tierra templada de los helechos.” The Arabic word for fern
is _feledschun_, _f_ being changed into _h_ in helechos according
to Spanish custom: perhaps the Arabic feledschun is connected with
“faladscha,” “it divides;” in allusion to the finely divided margins of
fern leaves or fronds. (Abu Zacaria Ebn el Awam, Libro de Agricultura,
traducido por J. A. Banqueri, T. ii. Madr. 1802, p. 736.)
The conditions of mild temperature and an atmosphere nearly saturated
with vapour, together with great equability of climate in respect to
both temperature and moisture, are fulfilled on the declivities of
the mountains, in the valleys of the Andes, and above all in the mild
and humid atmosphere of the southern hemisphere, where arborescent
ferns extend not only to New Zealand and Van Diemen Island (Tasmania),
but even to the Straits of Magellan and to Campbell Islands, or to
a latitude almost corresponding to that of Berlin in the northern
hemisphere. Of tree-ferns, Dicksonia squarrosa grows vigorously in
46° South latitude, in Dusky Bay (New Zealand); D. antarctica of
Labillardière in Tasmania; a Thyrsopteris in Juan Fernandez; an
undescribed Dicksonia with stems from 12 to 15 (nearly 13 to 16
English) feet in the south of Chili, not far from Valdivia; and a
Lomaria of rather less height in the Straits of Magellan. Campbell
Island is still nearer to the south pole, in 52-1/2° lat., and even
there the stem of the Aspidium venustum rises to 4 feet (4 feet 3
inches, English) before the fronds branch off.
The climatic relations under which Ferns in general flourish, are
manifested in the numerical laws of their quotients of distribution
taken in the manner alluded to in an earlier part of the present
volume. In the low plains of the great continents within the tropics,
the quotient for ferns is, according to Robert Brown, and according
to late researches, 1-20th of all the species of phænogamous plants
growing in the same region; in the mountainous parts of the great
continents in the same latitudes it is from 1-8th to 1-6th. But a very
different ratio is found in the small islands dispersed over the wide
ocean. The proportion of ferns to the whole number of Phanerogamæ
increases there in such a manner that in the groups of islands between
the tropics in the Pacific the ferns equal a fourth,--and in the
solitary far detached islands in the Atlantic Ocean, St. Helena,
and Ascension,--almost equal the half of the entire phænogamous
vegetation. (See an excellent memoir of D’Urville entitled Distribution
géographique des Fougères sur la surface du Globe, in the Annales
des Sciences Nat. T. vi. 1825, p. 51, 66, and 73). From the tropics
(where in the great continents D’Urville estimates the ratio generally
at 1:20) we see the relative frequency of ferns decrease rapidly in
the temperate zone. The quotients are: for North America and for the
British Islands 1/33, for France 1/58, for Germany 1/52, for the dry
parts of the south of Italy 1/74, and for Greece 1/84. Towards the
colder regions of the north we see the _relative_ frequency increase
again rapidly; that is to say, the number of species of ferns decreases
much more slowly than does the number of species of phænogamous plants.
At the same time, the luxuriance, abundance, and mass of individuals in
each species augments the illusive impression of _absolute_ numbers.
According to Wahlenberg’s and Hornemann’s Catalogues the relative
numbers of Filices are, for Lapland 1/25, for Iceland 1/18, and for
Greenland 1/12.
Such, according to the present state of our knowledge, are the natural
laws manifested in the distribution of the pleasing form of Ferns. But
it would seem as if in the family of Ferns, which has so long been
regarded as a cryptogamic family, we had quite recently arrived on the
traces of another natural law, a morphological one of propagation.
Count Leszczyc-Suminski, who happily unites the gift of microscopic
examination with distinguished artistic talent, has discovered in
the prothallium of ferns an organisation by which fructification is
effected. He distinguishes a bisexual arrangement in the ovule-like
cell on the middle of the theca, and in the ciliated antheridia or
spiral threads before examined by Nägeli. The fertilisation is supposed
to take place not by pollen tubes but by the moveable ciliated spiral
threads. (Suminski zur Entwickelungs-geschichte der Farrnkräuter, 1848,
S. 10-14.) According to this view, Ferns, as Ehrenberg expresses it
(Monatl. Berichte der Akad. zu Berlin, Januar 1848, S. 20), would be
produced by a microscopic fertilisation taking place on the prothallium
as a receptacle; and throughout the whole remainder of their often
arborescent development they would be flowerless and fruitless plants,
forming buds or bulbs; the spores or sori on the under side of the
frond not being seeds but flower buds.
[29] p. 28.--“_Liliaceæ._”
The principal seat of this form is Africa, where it is both most
varied and most abundant, and where these beautifully flowering
plants are assembled in masses and determine the aspect and character
of the country. The New Continent does, indeed, also possess superb
Alstromeriæ and species of Pancratium, Hæmanthus, and Crinum (we
augmented the first-named of these genera by nine, and the second by
three species); but these American Liliaceæ grow dispersed, and are
less social than our European Irideæ.
[30] p. 28.--“_Willow Form._”
Of the leading representative of this form, the Willow itself, 150
different species are already known. They are spread over the northern
hemisphere from the Equator to Lapland. They appear to increase in
number and diversity of form between the 46th and 70th degrees of
north latitude, and especially in the part of north of Europe where
the configuration of the land has been so strikingly indented by early
geological changes. Of Willows as tropical plants I am acquainted
with ten or twelve species, which, like the willows of the southern
hemisphere, are deserving of particular attention. As Nature seems
as it were to take pleasure in multiplying certain forms of animals,
for example Anatidæ (Lamellirostres) and Columbæ, in all the zones of
the earth; so are Willows, the different species of Pines, and Oaks,
no less widely disseminated: the latter (oaks) being always alike in
their fruit, though much diversified in the forms of their leaves. In
Willows, the similarity of the foliage, of the ramification, and of
the whole physiognomic appearance, in the most different climates,
is unusually great,--almost greater than even in Coniferæ. In the
southern part of the temperate zone of the northern hemisphere the
number of species of willows decreases considerably, yet (according to
the Flora atlantica of Desfontaines) Tunis has still a species of its
own resembling Salix caprea; and Egypt reckons, according to Forskäl,
five species, from the catkins of whose male flowers a medicine much
employed in the East, Moie chalaf (aqua salicis) is obtained by
distillation. The Willow which I saw in the Canaries is also, according
to Leopold von Buch and Christian Smith, a peculiar species, common
however to that group and to the Island of Madeira,--S. canariensis.
Wallich’s Catalogue of the plants of Nepaul and of the Himalaya cites
from the Indian sub-tropical zone thirteen species, partly described by
Don, Roxburgh, and Lindley. Japan has its indigenous willows, one of
which, S. japonica (Thunb.) is also found as a mountain plant in Nepaul.