Note 23 — PHYSIOGNOMY OF PLANTS.

p. 25.—“Needle-leaved trees.”

The family of Coniferæ holds so important a place by the number of individuals, by their geographical distribution, and by the vast tracts of country in the northern temperate zone covered with trees of the same species living in society, that we are almost surprised at the small number of species of which it consists,—even including members which belong to it in essential respects, but deviate from it in a degree by the shape of their leaves and their manner of growth (Dammara, Ephedra, and Gnetum, of Java and New Guinea). The number of known Coniferæ is not quite equal to three-fourths of the number of described species of palms; and there are more known Aroideæ than Coniferæ. Zuccarini, in his Beiträgen zur Morphologie der Coniferen (Abhandl. der mathem. physikal. Classe der Akademie der Wiss. zu München, Bd. iii. S. 752, 1837-1843), reckons 216 species, of which 165 belong to the northern and 51 to the southern hemisphere. Since my researches these proportionate numbers must be modified, as, including the species of Pinus, Cupressus, Ephedra, and Podocarpus, found by Bonpland and myself in the tropical parts of Peru, Quito, New Granada, and Mexico, the number of species between the tropics rises to 42. The most recent and excellent work of Endlicher, Synopsis Coniferarum, 1847, contains 312 species now living, and 178 fossil species found in the coal measures, the bunter-sandstone, the keuper, and the Jurassic formations. The vegetation of the ancient world offers to us more particularly forms which, by their simultaneous affinity with several different families of the present vegetable world, remind us that many intermediate links have perished. Coniferæ abounded in the ancient world: their remains, belonging to an early epoch, are found especially in association with Palms and Cycadeæ; but in the latest beds of lignite we also find pines and firs associated as now with Cupuliferæ, maples, and poplars. (Kosmos, Bd. i. S. 295-298, and 468-470; Engl. edit. p. 271-274, and lxxxix.)

If the earth’s surface did not rise to considerable elevations within the tropics, the highly characteristic form of needle-leaved trees would be almost unknown to the inhabitants of the equatorial zone. In common with Bonpland I have laboured much in the determination of the exact lower and upper limits of the region of Coniferæ and of oaks in the Mexican highlands. The heights at which both begin to grow (los Pinales y Encinales, Pineta et Querceta) are hailed with joy by those who come from the sea-coast, as indicating a climate where, so far as experience has hitherto shewn, the deadly malady of the black vomit (Vomito prieto, a form of yellow fever) does not reach. The lower limit of oaks, and more particularly of the Quercus xalapensis (one of the 22 Mexican species of oak first described by us), is on the road from Vera Cruz to the city of Mexico, a little below the Venta del Encero, 2860 (3048 E.) feet above the sea. On the western side of the highlands between the city of Mexico and the Pacific, the limit is rather lower down, for oaks begin to be found near a hut called Venta de la Moxonera, between Acapulco and Chilpanzingo, at an absolute elevation of 2328 (2480 E.) feet. I found a similar difference in the height of the lower limit of pine woods on the two-sides of the continent. On the Pacific side, in the Alto de los Caxones north of Quaxiniquilapa, we found this limit for Pinus Montezumæ (Lamb.), which we at first took for Pinus occidentalis (Swartz), at an elevation of 3480 (3709 E.) feet; while towards Vera Cruz, on the Cuesta del Soldado, pines are first met with at a height of 5610 (5950 E.) feet. Therefore both the kinds of trees spoken of above, oaks and pines, descend lower on the side of the Pacific than they do on the side of the Antillean sea. In ascending the Cofre di Perote, I found the upper limit of the oaks 9715 (10354 E.) feet, and that of the Pinus Montezumæ at 12138 (12936 E.) feet above the sea, or almost 2000 (2132 E.) feet higher than the summit of Etna. Considerable quantities of snow had fallen at this elevation in the month of February.

The more considerable the heights at which the Mexican Conifers are first met with, the more striking it appears to find in the Island of Cuba (where, indeed, on the borders of the torrid zone, northern breezes sometimes cool the atmosphere down to 6½° Reaumur, 46°.6 Fah.), another species of pine (P. occidentalis of Swartz), growing in the plains or on the low hills of the Isla de Pinos, intermixed with palms and mahogany trees (Swietenias). Columbus mentions a small pine wood (Pinal) in the journal of his first voyage (Diario del 25 de Nov. 1492), near Cayo de Moya, on the north-east of the Island of Cuba. In Hayti also, Pinus occidentalis descends from the mountains to the sea-shore, near Cape Samana. The trunks of these Pines, carried by the Gulf-stream to the Islands of Graciosa and Fayal in the Azores, were among the chief indications from which the great discoverer inferred the existence of unknown lands to the west. (See my Examen crit., T. ii. p. 246-259.) Is it true that in Jamaica, notwithstanding the height of its mountains, Pinus occidentalis is entirely wanting? We may also ask what is the species of Pinus found on the eastern coast of Guatimala, as P. tenuifolia (Benth.) probably belongs only to the mountains near Chinanta?

If we cast a general glance on the species which form the upper limits of arborescent vegetation in the northern hemisphere, from the frigid zone to the equator, we find, beginning with Lapland, that according to Wahlenberg, on the Sulitelma Mountain (lat. 68°) it is not needle-trees which form the upper limit, but that birches (Betula alba) extend much higher up than Pinus sylvestris;—whilst in the temperate zone, in the Alps (lat. 45¾°), Pinus picea (Du Roi) advances highest, leaving the birches behind; and in the Pyrenees (lat. 42½°), Pinus uncinata (Ram.) and P. sylvestris var. rubra: within the tropics, in lat. 19°-20° in Mexico, Pinus Montezumæ leaves far behind Alnus toluccensis, Quercus spicata, and Q. crassipes; while in the snow mountains of Quito at the equator, Escallonia myrtilloides, Aralia avicennifolia, and Drymis winteri, take the lead. The last-named tree, which is identical with Drymis granatensis (Mut.) and Wintera aromatica (Murray), presents, as Joseph Hooker has shewn (Flora Antarctica, p. 229), the striking example of the uninterrupted extension of the same species of tree from the most southern part of Tierra del Fuego and Hermit Island, where it was discovered by Drake’s Expedition in 1577, to the northern highlands of Mexico; or through a range of 86 degrees of latitude, or 5160 geographical miles. Where it is not birches (as in the far north), but needle trees (as in the Swiss Alps and the Pyrenees), which form the limit of arborescent vegetation on the highest mountains, we find above them, still nearer to the snowy summits which they gracefully enwreath with their bright garlands, in Europe and Western Asia, the Alp roses, the Rhododendra,—which are replaced on the Silla de Caracas and in the Peruvian Paramo de Saraguru by the purple flowers of another genus of Ericaceæ, the beautiful race of Befarias. In Lapland the needle-trees are immediately followed by Rhododendron laponicum; in the Swiss Alps by Rhododendron ferrugineum and R. hirsutum; in the Pyrenees by the R. ferrugineum only; and in the Caucasus by R. caucasicum. Decandolle found the Rhododendron ferrugineum growing singly in the Jura (in the Creux de Vent) at the moderate altitude of 3100 to 3500 (3304 to 3730 E.) feet, 5600 (5968 E.) feet lower down than its proper elevation. If we desire to trace the last zone of vegetation nearest to the snow line in the tropics, we must name, from our own observations, in the Mexican part of the tropical zone, Cnicus nivalis and Chelone gentianoides; in the cold mountain regions of New Granada, the woolly Espeletia grandiflora, E. corymbosa and E. argentea; and in the Andes of Quito, Culcitium rufescens, C. ledifolium, and C. nivale,—yellow flowering Compositæ which replace in the last-named mountains the somewhat more northerly Espeletias of New Granada, to which they bear a strong physiognomic resemblance. This replacement, the repetition of resembling or almost similar forms in countries separated either by seas or by extensive tracts of land, is a wonderful law of nature which appears to prevail even in regard to some of the rarest forms of vegetation. In Robert Brown’s family of the Rafflesieæ, separated from the Cytineæ, the two Hydnoras described by Thunberg and Drege in South Africa (H. africana and H. triceps) have their counterpart in South America in Hydnora americana (Hooker).

Far above the region of alpine plants, grasses, and lichens, and even above the limit of perpetual snow, the botanist sees with astonishment, both in the temperate and tropical zones, isolated phænogamous plants occur now and then sporadically on rocks which remain free from the general surrounding snowy covering, and which may possibly be warmed by heat ascending through open fissures. I have already spoken of the Saxifraga boussingaulti, which is found on the Chimborazo at an elevation of 14800 (15773 E.) feet; in the Swiss Alps, Silene acaulis has been seen at a height of 10680 (11380 E.) feet, being in the first-named case 600 (640 E.) feet, and in the second 2460 (2620 E.) feet above the limit of the snows, that limit being taken as it was in the two cases respectively at the time when the plants were found.

In our European Coniferæ, the Red and White Pine shew great and remarkable differences in respect to their distribution. While in the Swiss Alps the Red Pine (Pinus picea, Du Roi, foliis compresso—tetragonis; unfortunately called by Linnæus, and by most of the botanists of the present day, Pinus abies!) forms the upper limit of arborescent vegetation at a mean height of 5520 (5883 English) feet, only an occasional low growing mountain-alder (Alnus viridis, Dec., Betula viridis, Vill.) advancing now and then still nearer to the snow-line; the White Pine (Pinus abies, Du Roi, Pinus picea, Linn., foliis planis, pectinatodistichis, emarginatis) ceases, according to Wahlenberg, more than a thousand feet lower down. The Red Pine does not appear at all in the South of Europe, in Spain, the Appennines, and Greece; even on the northern slope of the Pyrenees it is seen only, as Ramond remarks, at great elevations, and is entirely wanting in the Caucasus. The Red Pine advances in Scandinavia farther to the north than the White Pine, of which last-named tree there is in Greece (on Mounts Parnassus, Taygetus, and Œta) a long needled variety (foliis apice integris, breviter mucronatis), the Abies Apollinis of Link. (Linnæa, Bd. xv. 1841, S. 529; and Endlicher, Synopsis Coniferarum, p. 96.)

On the Himalaya the Coniferæ are distinguished by the great thickness and height of their trunks, and by the length of their leaves. The Deodwara Cedar, Pinus deodara (Roxb.),—(properly, in Sanscrit, dêwa-dâru, timber of the Gods),—which is from 12 to 13½ feet thick, is the great ornament of the mountains. It grows in Nepaul to 11000 (11720 E.) feet above the level of the sea. More than 2000 years ago the Deodara supplied the materials for the fleet of Nearchus on the Hydaspes (the present Behut). In the valley of Dudegaon, north of the copper mines of Dhunpour in Nepaul, Dr. Hoffmeister, so early lost to science, found the Pinus longifolia of Royle (the Tschelu Pine) growing among tall stems of the Chamærops martiana of Wallich. (Hoffmeister’s Briefe aus Indien während der Expedition des Prinzen Waldemar von Preussen, 1847, S. 351.) Such an intermixture of pineta and palmata had excited the surprise of the companions of Columbus in the New Continent, as a friend and cotemporary of the Admiral, Petrus Martyr Anghiera, has informed us. (Dec. iii. lib. 10, p. 68.) I saw myself this intermixture of pines and palms for the first time on the road from Acapulco to Chilpanzingo. The Himalaya, like the Mexican highlands, has, besides Pines and Cedars, also the forms of Cypresses (Cupressus torulosa, Don), of Yews (Taxus wallichiana, Zuccar.), of Podocarpus (P. nereifolia, Robert Brown), and of Juniper (Juniperus squamata, Don., and J. excelsa, Bieberst; Juniperus excelsa is also found at Schipke in Thibet, in Asia Minor, in Syria, and in the Greek Islands). Thuja, Taxodium, Larix, and Araucaria, are forms found in the New Continent, but wanting in the Himalaya.

Besides the 20 species of Pines which we already know from Mexico, the United States of North America, which in their present extent reach to the Shores of the Pacific, have 45 described species, while Europe has only 15. There is a similar difference in respect to Oaks: i. e. greater variety of forms in the New Continent which extends continuously through a greater extent of latitude. The recent very exact researches of Siebold and Zuccarini have, however, completely refuted the previous belief, that many European species of Pines extend also across the whole of Northern Asia to the Islands of Japan, and even grow there, interspersed, as Thunberg has stated, with genuine Mexican species, the Weymouth Pine, Pinus Strobus of Linnæus. What Thunberg took for European Pines are wholly different and distinct species. Thunberg’s Red Pine (Pinus abies, Linn.) is P. polita, (Sieb.) and is often planted near Buddhistic temples; his common Scotch Fir (Pinus sylvestris) is P. Massoniana (Lamb.); his P. cembra (the German and Siberian pine with eatable seeds) is P. parviflora (Sieb.); his common Larch (P. larix) is P. leptolepis (Sieb.); and his supposed Taxus baccata, the fruits of which are eaten by Japanese courtiers in case of long-protracted court ceremonials, (Thunberg, Flora Japonica, p. 275), constitutes a distinct genus, and is the Cephalotaxus drupacea of Siebold. The Islands of Japan, notwithstanding the vicinity of the Continent of Asia, have a very distinct character of vegetation. Thunberg’s supposed Japanese Weymouth Pine, (Pinus Strobus) which would offer an important phenomenon, is only a planted tree, and is besides quite distinct from the American species of Pine. It is Pinus korajensis (Sieb.), and has been brought to Nipon from the peninsula of Corea, and from Kamtschatka.

Of the 114 species of the Genus Pinus with which we are at present acquainted, not one belongs to the Southern Hemisphere, for the Pinus merkusii described by Junghuhn and De Vriese belongs to the part of the Island of Sumatra which is north of the Equator, to the district of the Battas; and Pinus insularis (Endl.) although it was at first given in Loudon’s Arboretum as P. timoriensis, really belongs to the Philippines. Besides the Genus Pinus, the Southern hemisphere, according to the present state of our now happily advancing knowledge of the geography of plants, is entirely without species of Cupressus, Salisburia (Gingko), Cunninghamia (Pinus lanceolota, Lamb.) Thuja, (one of the species of which, Th. gigantea, Nutt., found on the banks of the Columbia, has a height of above 180 Eng. feet), Juniperus, and Taxodium (Mirbel’s Schubertia). I include the last-named genus with the less hesitation, as a Cape of Good Hope plant (Sprengel’s Schubertia capensis) is no Taxodium, but constitutes a genus of itself, Widringtonia, (Endl.) in quite a different division of the family of Coniferæ.

This absence, from the Southern Hemisphere, of true Abietineæ, Juniperineæ, Cupressineæ, and all the Taxodineæ, as well as of Torreya, Salisburia adiantifolia, and Cephalotaxus from among the Taxineæ, recalls forcibly the obscurity which still prevails in the conditions which have determined the original distribution of vegetable forms, a distribution which cannot be sufficiently and satisfactorily explained solely by similarity or diversity of soil, thermic relations, or meteorological phenomena. I remarked long ago that the Southern Hemisphere for example has many plants belonging to the natural family of Rosaceæ, but not a single species of the genus Rosa. We learn from Claude Gay that the Rosa chilensis described by Meyen is only a wild variety of the Rosa centifolia (Linn.), which has been for thousands of years a European plant. Such wild varieties, (i. e. varieties which have become wild) occupy large tracts of ground in Chili, near Valdivia and Osorno. (Gay, Flora Chilensis, p. 340.)

In the tropical region of the Northern hemisphere we also found only one single native rose, our Rosa montezumæ, in the Mexican highlands near Moran, at an elevation of 8760 (9336 Engl.) feet. It is one of the singular phenomena in the distribution of plants, that Chili, which has Palms, Pourretias, and many species of Cactus, has no Agave; although A. americana grows luxuriantly in Roussillon, near Nice, near Botzen and in Istria, having probably been introduced from the New Continent since the end of the 16th century, and in America itself forms a continuous tract of vegetation from Northern Mexico across the isthmus of Panama to the Southern part of Peru. I have long believed that Calceolarias were limited like Roses exclusively to one side of the Equator; of the 22 species which we brought back with us, not one was collected to the north of Quito and the Volcano of Pichincha; but my friend Professor Kunth remarks that Calceolaria perfoliata, which Boussingault and Captain Hall found at Quito, advances to New Granada, and that this species, as well as C. integrifolia of Santa Fé de Bogotá, were given by Mutis to the great Linnæus.

The species of Pinus which are so frequent in the tropical Antilles and in the tropical mountains of Mexico do not pass the isthmus of Panama, and are not found in the equally mountainous parts of the tropical portion of South America, and in the high plains of New Granada, Pasto, and Quito. I have been both in the plains and on the mountains from the Rio Sinu, near the isthmus of Panama, to 12° S. lat.; and in this tract of almost 1600 geographical miles the only forms of needle-trees which I saw were a Taxus-like species of Podocarpus with stems 60 (64 Eng.) feet high (Podocarpus taxifolia), growing in the Pass of Quindiu and in the Paramo de Saraguru, in 4° 26´ north, and 3° 40´ south latitude; and an Ephedra (E. americana) near Guallabamba, north of Quito.

Among the Coniferæ there are common to the northern and southern hemispheres the genera Taxus, Gnetum, Ephedra, and Podocarpus. The last-named genus was distinguished from Pinus long before L’Heritier by Columbus himself, who wrote on the 25th of November, 1492: “Pinales en la Serrania de Haiti que no llevan piñas, pero frutos que parecen azeytunos del Axarafe de Sevilla.” (See my Examen crit. T. iii. p. 24.) There are species of Taxus from the Cape of Good Hope to 61° N. lat. in Scandinavia, or through more than 95 degrees of latitude; Podocarpus and Ephedra extend almost as far. In Cupuliferæ, the species of oak which we are accustomed to regard as a northern form do not indeed pass beyond the equator in South America, but in the Indian Archipelago they re-appear in the southern hemisphere in the Island of Java. To the southern hemisphere belong exclusively ten genera of Coniferæ, of which I will name here only the principal: Araucaria, Dammara (Agathis Sal.), Frenela (with eighteen New Holland species), Dacrydium and Lybocedrus, which is found both in New Zealand and at the Straits of Magellan. New Zealand has one species of the genus Dammara (D. australis) and no Araucaria. In New Holland in singular contrast the case is opposite.

Among tree vegetation, it is in the form of needle-trees that Nature presents to us the greatest extension in length (longitudinal axis): I say among tree vegetation, because, as we have already remarked, among oceanic Algæ, Macrocystis pyrifera, which is found between the coast of California and 68° S. lat., often attains from 370 to 400 (about 400 to 430 Eng.) feet in length. Of Coniferæ, (setting aside the six Araucarias of Brazil, Chili, New Holland, Norfolk Island, and New Caledonia), the loftiest are those which belong to the northern temperate zone. As in the family of Palms we found the most gigantic, the Ceroxylon andicola, above 180 French (192 English) feet high, in the temperate mountain climate of the Andes, so the loftiest Coniferæ belong, in the northern hemisphere, to the temperate north-west coast of America and to the Rocky Mountains (lat. 40°-52°); and in the southern hemisphere to New Zealand, Tasmania or Van Diemen Island, the south of Chili and Patagonia (between 43° and 50° latitude). The most gigantic forms belong to the genera of Pinus, Sequoia (Endl.), Araucaria, and Dacrydium. I propose to name only those species which not only attain but often exceed 200 French feet (213 Eng.) In order to afford a standard of comparison, it should be remarked that in Europe the tallest Red and White Pines, the latter especially, attain about 150 or 160 (160-170 Eng.) feet; that, for example, in Silesia the Pine of the Lampersdorf Forest near Frankenstein enjoys great celebrity, although, with a circumference of 17 English feet, its height is only 153 Prussian, or 148 French, or 158 English feet. (Compare Ratzeburg, Forstreisen, 1844, S. 287.)

Pinus grandis (Douglas) in New California attains 224 English feet.

Pinus frémontiana (Endl.), also in New California, probably attains the same stature as the preceding. (Torrey and Frémont, Report of the Exploring Expedition to the Rocky Mountains in 1844, p. 319.)

Dacrydium cupressinum (Solander), from New Zealand, 213 English feet.

Pinus lambertiana (Dougl.), in North-west America, 224-235 English feet.

Araucaria excelsa (R. Brown), the Cupressus columnaris of Forster, in Norfolk Island and the surrounding rocky islets, 181-224 English feet. The six species of Araucaria which have become known to us hitherto, fall, according to Endlicher, into two groups:

a. The American group (Brazil and Chili): A. brasiliensis (Rich.), between 15° and 25° 8. lat.; and A. imbricata (Pavon), between 35° and 50° S. lat., the latter growing to 234-260 English feet.

b. The Australian group: A. bidwilli (Hook.) and A. cunninghami (Ait.) on the east side of New Holland; A. excelsa on Norfolk Island, and A. cookii (R. Brown) in New Caledonia. Corda, Presl. Göppert, and Endlicher, have already discovered five species of Araucarias belonging to the ancient world in the lias, in chalk, and in beds of lignite (Endlicher, Coniferæ fossiles, p. 301.).

Pinus Douglasii (Sabine), in the valleys of the Rocky Mountains and on the banks of the Columbia River (north lat. 48°-52°). The meritorious Scotch botanist from whom this tree is named perished in 1833 by a dreadful death in collecting plants in the Sandwich Islands, where he had arrived from New California. He fell inadvertently into a pit in which a fierce bull belonging to the cattle which have become wild had previously fallen, and was gored and trampled to death. By exact measurement a stem of Pinus Douglasii was 57½ English feet in girth at 3 feet above the ground, and its height was 245 English feet. (See Journal of the Royal Institution, 1826, p. 325.)

Pinus trigona (Rafinesque), on the western declivity of the Rocky Mountains, described in Lewis and Clarke’s Travels to the Source of the Missouri River and across the American Continent to the Pacific Ocean (1804-1806), 1814, p. 456. This gigantic Fir was measured with great care; the trunks were often 38 to 45 English feet in girth, 6 feet above the ground: one tree was 300 English feet high, and the first 192 feet were without any division into branches.

Pinus Strobus grows in the eastern parts of the United States of North America, especially on the east of the Mississipi; but it is found again in the Rocky Mountains from the sources of the Columbia to Mount Hood, or from 43° to 54° N. lat. It is called in Europe the Weymouth Pine and in North America the White Pine: its ordinary height does not exceed 160 to 192 Eng. feet, but several trees of 250 to 266 Eng. feet have been seen in New Hampshire. (Dwight, Travels, Vol. i. p. 36; and Emerson’s Report on the Trees and Shrubs growing naturally in the Forests of Massachusetts, 1846, p. 60-66.)

Sequoia gigantea (Endl.), Condylocarpus (Sal.) from New California; like Pinus trigona, about 300 English feet high.

The nature of the soil, and the circumstances of heat and moisture on which the nourishment of plants depend, no doubt influence the degree to which they flourish, and the increase in the number of individuals in a species; but the gigantic height attained by the trunks of a few among the many other nearly allied species of the same genus, depends not on soil or climate; but, in the vegetable as well as in the animal kingdom, on a specific organisation and inherent natural disposition. I will cite as the greatest contrast to the Araucaria imbricata of Chili, the Pinus Douglasii of the Columbia River, and the Sequoia gigantea of New California, which is from 245 to 300 Eng. feet in height,—not a plant taken from among a vegetation stunted by cold either of latitude or elevation, as is the case with the small Willow-tree, two inches in height, (Salix arctica),—but a small phænogamous plant belonging to the fine climate of the southern tropic in the Brazilian province of Goyaz. The moss-like Tristicha hypnoïdes, from the monocotyledonous family of the Podostemeæ, hardly reaches the height of 3 lines (²⁷⁄₁₀₀ths, or less than three-tenths of an English inch.) “En traversant le Rio Claro dans la Province de Goyaz,” says an excellent observer, Auguste de St.-Hilaire, “j’aperçus sur une pierre une plante dont la tige n’avoit pas plus de trois lignes de haut et que je pris d’abord pour une mousse. C’étoit cependant une plante phanérogame, le Tristicha hypnoïdes, pourvue d’organes sexuels comme nos chênes et les arbres gigantesques qui à l’entour élevaient leur cimes majestueuses.” (Auguste de St.-Hilaire, Morphologie Végétale, 1840, p. 98.)

Besides the height of their stems, the length, breadth, and position of the leaves and fruit, the form of the ramification aspiring or horizontal, and spreading out like a canopy or umbrella,—the gradations of colour, from a fresh green or silvery grey to a blackish-brown, all give to Coniferæ a peculiar physiognomy and character. The needles of Douglas’s Pinus lambertiana from North-west America are five French inches long; those of Pinus excelsa of Wallich, on the southern declivity of the Himalaya, near Katmandoo, seven French inches; and those of P. longifolia (Roxb.), from the mountains of Kashmeer, above a French foot long. In one and the same species the length of the leaves or needles varies in the most striking manner from the influence of soil, air, and elevation above the level of the sea. In travelling in an east and west direction through eighty degrees of longitude (above 3040 geographical miles), from the mouth of the Scheldt through Europe and the north of Asia to Bogoslowsk in the northern Ural and Barnaul beyond the Obi, I have found differences in the length of the needles of our common Fir (Pinus sylvestris) so great, that sometimes a traveller may be misled by the shortness and rigidity of the leaves, to think that he has discovered a new species allied to the Mountain Pine, P. rotundata (Link), P. uncinata (Ram.) Link has justly remarked (Linnæa, Bd. xv. 1841, S. 489) that such instances may be regarded as transitions to Ledebour’s P. sibirica of the Altai.

In the Mexican highlands I have looked with particular pleasure on the delicate cheerful green of the Ahuahuete, Taxodium distichum (Rich.), Cupressus disticha (Linn.), which, however, is much given to shedding its leaves. In this tropical region the above-mentioned tree, (of which the Aztec name signifies water-drum, from atl, water, and huehuetl, a drum, the trunk swelling to a great thickness), flourishes 5400 and 7200 (5755 and 7673 English) feet above the level of the sea, while in the United States of North America it is found in the low grounds of the cypress swamps of Louisiana, in the 43d parallel. In the Southern States of North America the Taxodium distichum (Cyprès chauve) reaches, as in the Mexican highlands, the height of 120 (128 English) feet, and the enormous thickness of 30 to 37 (32 to 39 English) feet, in diameter measured near the ground. (Emerson, Report on the Forests, pp. 49 and 101). The roots present the striking phenomenon of woody excrescences which project from 3 to 4½ feet above the earth, and are conical and rounded, and sometimes tabular. Travellers have compared these excrescences in places where they are very numerous to the grave tablets in a Jewish burying-ground. Auguste de St. Hilaire remarks with much acuteness:—“Ces excroissances du Cyprès chauve, ressemblant à des bornes, peuvent être regardées comme des exostoses, et comme elles vivent dans l’air, il s’en échapperoit sans doute des bourgeons adventifs, si la nature du tissu des plantes conifères ne s’opposoit au développement des germes cachés qui donnent naissance à ces sortes de bourgeons.” (Morphologie végétale, p. 91). A singularly enduring power of vitality in the roots of trees of this family is shown by a phenomenon which has excited the attention of vegetable physiologists, and appears to be of only very rare occurrence in other dicotyledonous trees. The remaining stumps of White Pines which have been cut down continue for several years to make fresh layers of wood, and to increase in thickness, without putting forth new shoots, leaves, or branches. Göppert believes that this only takes place by means of root nourishment received by the stump from a neighbouring living tree of the same species; the roots of the living individual which has branches and leaves having become organically united with those of the cut tree by their having grown together. (Göppert, Beobachtungen über das sogenannte Umwallen der Tannenstöcke, 1842, S. 12). Kunth, in his excellent new “Lehrbuch der Botanik,” objects to this explanation of a phenomenon which was known, imperfectly, so early as Theophrastus. (Hist. Plant. lib. iii. cap. 7, pp. 59 and 60, Schneider.) He considers the case to be analogous to what takes place when metal-plates, nails, carved letters, and even the antlers of stags, become enclosed in the wood of a growing tree. “The cambium, i. e. the viscid secretion out of which new elementary organs are constructed either of woody or cellular tissue, continues, without reference to the buds (and quite apart from them), to deposit new layers of wood on the outermost layer of the ligneous substance.” (Th. i. S. 143 and 166.)

The relations which have been alluded to, between elevation above the level of the sea and geographical and thermal latitude, manifest themselves often when we compare the tree vegetation of the tropical part of the chain of the Andes with the vegetation of the north-west coast of America, or with that of the shores of the Canadian Lakes. Darwin and Claude Gay have made the same remark in the Southern Hemisphere, in advancing from the high plains of Chili to Eastern Patagonia and Tierra del Fuego, where they found Drymis winteri and forests of Fagus antarctica and Fagus forsteri forming a uniform covering throughout long continuous lines running from north to south and descending to the low grounds. We find even in Europe small deviations (dependent on local causes which have not yet been sufficiently examined), from the law of constant ratio as regards stations or habitat of plants between elevation above the sea and geographical latitude. I would recall the limits, in respect to elevation, of the birch and the common fir in a part of the Swiss Alps, on the Grimsel. The fir (Pinus sylvestris) extends to 5940, and the birch (Betula alba) to 6480 French (6330 and 6906 English) feet; above the birches there is a higher line of Pinus cembra, whose upper limit is 6890 (7343 English) feet. Here, therefore, we have the birch intervening between two zones of Coniferæ. According to the excellent observations of Leopold Von Buch, and the recent ones of Martins, who also visited Spitzbergen, the following geographical limits were found in Lapland:—Pinus sylvestris extends to 70°; Betula alba to 70° 40´; and Betula nana quite up to 71°; Pinus cembra is altogether wanting in Lapland. (Compare Unger über den Einfluss des Bodens auf die Vertheilung der Gewächse, S. 200; Lindblom, Adnot. in geographicam plantarum intra Sueciam distributionem, p. 89; Martins, in the Annales des Sciences naturelles, T. xviii. 1842, p. 195).

If the length and arrangement of the needle-shaped leaves go far to determine the physiognomic character of Coniferæ, this character is still more influenced by the specific differences in the breadth of the needles, and the degree of development of the parenchyma of the appendicular organs. Several species of Ephedra may be called almost leafless; but in Taxus, Araucaria, Dammara (Agathis), and the Salisburia adiantifolia of Smith (Gingko biloba, Linn.), the surfaces of the leaves become gradually broader. I have here placed the genera in morphological succession. The specific names first chosen by botanists testify in favour of such a succession. The Dammara orientalis of Borneo and Java, often above ten feet in diameter, was first called loranthifolia; and Dammara australis (Lamb.) of New Zealand, which is 140 (149 English) feet high, was first called zamæfolia. In both these species of trees the leaves are not needles, but “folia alterna oblongo-lanceolata, opposita, in arbore adultiore sæpe alterna, enervia, striata.” The under surface of the leaves is thickly set with porous openings. This passage or transition of the appendicular system from the greatest contraction to a broad-leaved surface, like all progression from simple to compound, has at once a morphological and a physiognomic interest (Link, Urwelt, Th. I. 1834, S. 201-211). The short-stalked, broad, cleft leaf of the Salisburia (Kämpfer’s Gingko) has also its breathing pores only on the under side of the leaf. The original native country of this tree is unknown to us. By the connection and intercourse of Buddhistic communities it early passed from the temple-gardens of China to those of Japan.

In travelling from a port on the Pacific to Mexico, on our way to Europe, I witnessed the singular and painful impression which the first sight of a pine forest near Chilpanzingo made on one of our companions, who, born at Quito under the equinoctial line, had never seen needle trees, or trees with “folia acerosa.” It seemed to him as if the trees were leafless; and he thought that as we were travelling towards the cold North, he already recognised in this extreme contraction of the vegetable organs the chilling and impoverishing influence of the pole. The traveller whose impressions I here describe, whose name neither my friend Bonpland or myself can pronounce without regret, was Don Carlos Montufar (son of the Marquis of Selvalegre), an excellent young man, whose noble and ardent love of freedom led him a few years later, in the war of independence of the Spanish Colonies, to meet courageously a violent death, of which the dishonour did not fall on him.