94. p. 227—“Pothos plants, Aroideæ.”

Caladium and Pothos are forms appertaining exclusively to the tropical world, whilst the different species of Arum belong more to the temperate zone. Arum italicum, A. dracunculus, and A. tenuifolium advance as far as Istria and Friuli. No Pothos has hitherto been discovered in Africa. The East Indies possess several species of this genus (P. scandens and P. pinnata), which have a less beautiful physiognomy and are of less luxuriant growth than the American Pothos plants. We discovered a beautiful true arborescent Aroidea (Caladium arboreum), having a stem from 16 to more than 21 feet in height, near the convent of Caripe, east of Cumana. Beauvois found a singular Caladium (Culcasia scandens) in the kingdom of Benin.^[PY] In the Pothos form the parenchyma occasionally expands to so great a degree that the leaf-surface becomes perforated with holes, as in Calla pertusa (Kunth), and Dracontium pertusum (Jacquin), which we collected in the forests of Cumana. It was the Aroideas which first drew attention to the remarkable phenomenon of the fever-heat evolved by certain plants during the period of their inflorescence, and which even sensibly affects the thermometer, and is connected with a great and temporary increase in the absorption of oxygen from the atmosphere. Lamarck, in 1789, observed this increase of temperature in the Arum italicum. According to Hubert and Bory de St. Vincent, the vital heat of the Arum cordifolium rises in the Isle of France to 110° or 120°, whilst the temperature of the surrounding air is only 66°.2 Fahr. Even in Europe, Becquerel and Breschet found a difference of 39°.4. Dutrochet observed a paroxysm,—a rhythmical decrease and increase of vital heat,—which appeared by day to attain a double maximum. Théodore de Saussure remarked analogous augmentations of heat, although only of 1°.1 and 1°.8 Fahr., in other families of plants; as, for instance, in Bignonia radicans and Cucurbita pepo. In the latter, the male plant exhibited a greater increase of temperature than the female, when measured by a very sensitive thermoscopic apparatus. Dutrochet—whose early death is greatly to be regretted, on account of the important services he rendered to physics and vegetable physiology—likewise observed,^[PZ] by means of thermo-magnetic multiplicators, a vital heat of 0°.25 to 0°.67 Fahr. in many young plants (Euphorbia lathyris, Lilium candidum, Papaver somniferum), and even among funguses, in many species of Agaricus and Lycoperdon. This vital heat disappeared at night, but not by day, even when the plants were placed in the dark.

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.

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]

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.

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]

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.

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.

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.

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.

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.

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.

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.”