Chapter III: Front Matter (3)

_Eucalyptus_, which occupies such a large place in Australian vegetation, may be said to be the sacred tree with the natives; it shadows the tombs of the savage inhabitants of these countries. Sir Thomas Mitchell, the traveler to whom we owe the first scientific description of Australia, has given a remarkable picture of “these groves of death,” which are daily becoming more and more rare, and will disappear under the influence of European colonization. He relates that these groves mark the centre of the patrimonial land of each great Australian tribe. Little _tumuli_ of grass, and sandy footpaths, surround the clumps of these funereal squares, over which spreads the shadow of the _Eucalyptus_ and _Xanthorrhæa._ If to the magnificent _Eucalyptus_ and simple-leaved _Acacia_, which predominate in the forests and give quite a special character to the vegetation, we add the _Xanthorrhæa_, with its thick stem, long, narrow, linear leaves, curved and spreading at the summit, from the centre of which rises an elongated stem, terminated by a spike of robust flowers; the _Casuarina_, with long, pendent, and drooping boughs, most delicately articulated; _Araucaria excelsa_, whose column-like trunk and verticillate branches rise to the height of ninety or a hundred feet; the elegant _Epacridaceæ_, with flowers so varied; a vast number of pretty _Leguminosæ_, which now add to the riches of our hothouses; more than 120 terrestrial _Orchidaceæ_, nearly all belonging to genera peculiar to Australia, we shall have an idea of the vegetation which covers and decorates in so original a way the shores of New Holland.

The large islands of New Zealand almost correspond in latitude with the zone which we have been examining. These islands are the nearest land (considering Van Diemen’s Land as part of Australia), and are interesting as being the exact antipodes of western Europe, and because they repeat as it were our Mediterranean region on the other side of the globe. While resembling it in climate, however, the native vegetation has its own characteristics. It has some features in common with Australia and the tropics.

In the large island of Ika-na-Nawi there are immense forests of _Lianes_ and interlacing shrubs, which render them impenetrable. In these forests there exist, no doubt, trees of gigantic dimensions, for the canoes of the natives are sometimes as much as sixty feet long, and from three to four broad, all hollowed out of one trunk. At from two to four miles from the coast Messrs. Richard and Lesson saw large spaces, very low and probably marshy, covered with great masses of green trees, of which the _Dacrydium cupressinum_ and _Podocarpus dacrydiodes_ and some others, form the principal species. The European is surprised to meet there many familiar plants, or species closely allied to them, such as _Senecio_, _Veronica_, rushes, _Ranunculus acris_, etc. On the other hand, several plants peculiar to New Zealand grow abundantly in these localities, such, among others, as the _Phormium tenax_, called by Europeans New Zealand Flax, because its fibres furnish a very strong thread, much used in the manufacture of certain fabrics.

Ferns form a tenth of the number of species in the whole vegetation of New Zealand; among Monocotyledons are _Graminaceæ_ and _Cyperaceæ_; among Dicotyledons, _Umbelliferæ_, _Cruciferæ_, and _Onagrariaceæ_. New Zealand only furnishes a small number of alimentary plants. The aboriginal inhabitants of this archipelago, for the most part ichthyophagous, were long reduced to the feculent root of a fern, the _Pteris esculenta_, for food, when they could not obtain fish. None of their trees produce large fruit. The taro (_Caladium esculentum_) and the sweet potato (_Convolvulus Batatas_) also serve as nourishment to the inhabitants of these countries. It is to be remarked that European vegetables, introduced into New Zealand by sailors, are propagated there with such facility that the aspect of the ground, as well as conditions of life, are greatly modified. Among the vegetables proper to the archipelago in question we may note the _Corypha australis_ among the palms; arborescent species of _Dracæna_, forests of _Coniferæ_, with large leaves, such as _Dammara_, and _Metrosideros_ among the _Myrtaceæ_.

ZONES OF VEGETATION
--M. J. SCHLEIDEN

If, from the snow-covered ice-plains of the extreme north, where the Red-snow Alga alone remind us of the existence of vegetable organization, we turn toward the south, a girdle first expands before us, in which mosses and lichens clothe the soil, and a peculiar vegetation of low plants with subterranean, perennial stems, and generally large, handsome flowers, the so-called Alpine plants, gives a special character to Nature. Almost all the plants form little, flattened, separate tufts; _Pyrola_, _Andromeda_, _Pedicularis_, _Cochlearia_, poppies, crow-foots, and others are the characteristic genera of this flora, in which no tree, no shrub flourishes. Leaving this region, which botanists call the region of Mosses and Saxifrages, or, after one of the founders of Geographical Botany, Wahlenberg’s region, we go southward, and at first we see little low bushes of birches, then more compacted woods, into which the pines and other coniferous trees assemble, and we at last find ourselves in a second great zone of vegetation which is characterized by the woods consisting almost exclusively of conifers, which thus impress a peculiar character upon the flora; firs and pines, Siberian stone-pines and larches form great widely extended masses of forest; by brooks and on damp soil occur the willow and the alder. On dry hills grow the reindeer lichen and Iceland moss. In the cranberry, cloud-berry, and the currant Nature gives spontaneously, though sparingly, food; and a rich flora of variegated flowers serves for the decoration of the zone, which stretches, in Scandinavia, to the northern limit of the cultivation of wheat, but in Russia and Asia, almost to Kazan and Yakutsk; we will call it the zone of the conifers. Even in the neighborhood of Drontheim, the culture of fruits begins, though sparingly; soon appears the sturdy oak, called, with rather too much poetic license, “the German”; in Schoonen, Zealand, Schleswig, and Holstein flourish the first woods of beech. In about the latitude of Frankfort-on-the-Main, another tree joins company, which, in its bold, picturesque mode of branching, takes its stand beside the oak--which in the beauty of its foliage, as well as the utility of its fruit, it far surpasses--namely, the noble chestnut. The Pyrenees, the Alps, and the Caucasus form the southern limit of the zone, in the more eastern portion of which the lime and the elm contribute so abundantly to the composition of the forests that the former even withstands the devastation which the Esthonians make in the manufacture of their shoes from its bass. In the hop, the ivy, and the clematis we find here the first representation of the tropical climbers. The smiling green of the meadows alternates with the gloomy shadows of the forests; and man has taken possession of the earth, restraining the wild vegetation to that absolutely needful for wood and hay, and rich crops reward his industry. We leave this zone of the deciduous woods to scale the rocky barrier of the Alps. Here suddenly appear quite different plants; with the great woods of trees, the coriaceous shining leaves of which last through the mild winter, and round the mighty stems of which climb the vine and flame-colored Bignonias, unite the smaller bushes of myrtle, arbutus, and pistachio. Here and there the dwarf-palm is met with; labiate plants and crucifers, and fair-flowered rock-roses replace in summer the spring flora of scented hyacinth and narcissus; but rarely, even in the most favored spots, is the eye dazzled by the brilliancy of evergreen leaves, or the glaring play of color of the naked, jagged mountain chains, gladdened by the mild radiance of verdant meadows. In recompense, mankind has, in this zone of evergreen woods, seized upon the fruit of the Hesperides. It is

“the land where the Citrons blow,
Through the dark-green leaves the gold Oranges glow.”

But onward, ever onward, strives the insatiable son of Iapetus; no legend of African deserts, no death-news of the many adventurous travelers who have gone forth to seek the source of the Niger, frighten him back. On the west coast of Africa, in the Canary Isles, is, indeed, no longer found the gigantic dog, from which, as Pliny told, the islands derived their name, but Flora gives for booty richest treasures which she, by aid of the tropical sun, has succeeded in extracting from the soil, moistened by the vapors of the ocean. Round sycamores twine mighty cissus stems; capers and bauhinias interlace in the thickets of balsamic shrubs. The slender date-palm soars aloft, and the baobab grows up into gigantic masses of wood. The wondrous cactus-like forms of the leafless spurges, distinguished by their poisonous or pleasant-flavored, sweet milk, as the case may be, betray a peculiar formative power in Nature; and the dragon-tree in the garden of Orotava,[3] in Teneriffe, a gigantic arborescent lily-plant, recounts to the musing listener the traditions of thousands of years.

Six zones of vegetation have we thus passed through, in which the continually increasing temperature of the climate called forth ever a different, ever a more luxuriant vegetation, and we conclude our wanderings, after a short rest under the five-thousand-yeared Dracænas, by climbing the Pic of Teyde. Man has taken possession of the soil of the plain at its foot and dislodged the original vegetation. Through vineyards and maize-fields we ascend, till the shades of the evergreen bay-laurel surround us. Trees of the lace-bark tribe and similar plants succeed; we wander for a time through a _zone of evergreen forest trees_. At a height of 4,000 feet we lose the plants which had so far accompanied us. A very small number of peculiar plants mark a quickly traversed _zone of deciduous trees_, and we come among the resinous trunks of the Canary pine. A _zone of conifers_ shield us from the sun’s rays up to a height of 6,000 feet, then the vegetation suddenly becomes low--from humble bushes it passes into a flora which bears all the characters of the Alpine plants, till finally the naked rock sets a limit to all organic life, and no snow and ice bedeck the summit of the mountain, only because its height of 12,236 feet does not, in a position so near the tropics, extend up to the region of eternal snow. Counting by the limits of vegetation, we have resurveyed in a few hours’ climb the wide way from Spitzbergen to the Canaries, an extent of more than fifty degrees of latitude.

The plant is dependent on the condition of the soil, in the widest sense of the word, on the store of nutriment it contains, and on all that influences the chemical process of formation, consequently, above all, upon a determinate temperature. The universal, indispensable nutrient substance of plants, and, at the same time, the matter by means of which all the rest are conveyed into it, is water. Without water there is no vegetation. The orchidaceous plants of the tropical forest let their peculiarly constructed roots hang down from the branch to which they cling in the warm, moist atmosphere, and absorb water in the form of vapor. Our water-lilies and the proper bog-plants will only flourish when surrounded by liquid water, or, at least, with their roots dipping in it. The case is quite different with the great majority of plants; they have to extract their nutriment from the earth, which contains the moisture to be absorbed into them in a peculiar condition. If to these three classes of air, water, and earth-plants we add one more, namely, the true parasites, which, like our dodder, draw their organized nutriment from other plants, we have obtained the principal divisions of stations.

Every soil which bears plants contains also in its composition all the substances required by all plants, only the proportions differ, and the predominance of silex, lime, or common salt must consequently favor especially the growth of grasses, pulses, or shore-plants, although these are by no means exclusively confined to the proper sandy or calcareous soils, or to the seaside. In addition to the chemical conditions, there is yet another which modifies the former and, where it brings about the same actions, contributes to chain particular plants so much the more firmly, exclusively to particular soils, or contrariwise also contributes to conceal or obliterate the connection between plants and the chemical nature of the soil. This consists in the mechanical condition and physical peculiarities of the soil. There are plants which will only settle on unbroken _rocks_, which when the other conditions coincide, spring from these rocks over on to our _walls_, like the Wall Rue Spleenwort,[4] a little fern, the name of which denotes its station. Others occur only where weathering has broken up the solid rock into small fragments, _drift_ plants, which, clinging to mankind, select _rubbish heaps_, which most resemble their natural station; our great nettle and henbane may serve as examples. Lastly, other plants grow only where the rocks have been reduced to fine powder, in _sand_ or in the fine-grained _clay_ produced by chemical decomposition. The so-called German Sarsaparilla, the sea-reed, is an example of the first condition, but there is no definite condition corresponding to it in the vicinity of human habitations. Clay, on the other hand, stands beside the black substance humus, resulting from the decomposition of organic matter. Both rich in soluble salts, important to vegetation, both distinguished in regard to their property of absorbing from the atmosphere, and thus conveying to the roots of plants gases and aqueous vapor, they cause, singly or in combination, the most luxuriant vegetation. We thus obtain three stages in reference to the qualities of the soil-pure earths, wholly devoid of vegetation; mixed earths, without clay or humus, with an arid but characteristic vegetation; and lastly, soil rich in clay and humus, with the greatest abundance and variety of plants.

Australia has, in common with Europe, a very common plant, the daisy (_Bellis perennis_). The same little flower is found in northern Asia, in some regions in Africa and South America, and where it occurs it climbs the mountains from the level of the sea up to the snow-limit. The little enchanter’s nightshade, the delicate Linnæa, the bittersweet, the bird’s knot-grass, the blue gentian, the dwarf birch, and the herbaceous willow, and several others, are indigenous both in Europe and North America. The common self-heal, the duckweed, and our reed grow in New Holland. The bog-moss covers the moors of Peru and New Granada, as well as those of the Hartz and of Dovrefjeld in Norway. The brownish Parmelia, which clothes all our walls in Germany, palings, and old trees, is no less present on the only ninety-year-old Yorullo in Mexico. The bluish bristle-grass, which is one of the commonest garden and field weeds on sandy soils with us, grows also in the interior of Brazil on suitable soil. A characteristic plant of the seashores of Northern Europe and the vicinity of salt-springs, _Ruppia martima_, grows equally on the northern coast of Germany, in Brazil, and the East Indies. But it is needless to accumulate examples, for these so hasten to present themselves that the view finds some support in observation which assumes that every plant must exist in every part of the globe where the known conditions of its vegetation are present.

The little daisy (_Bellis perennis_) exhibits a certain wilfulness. It is wanting all through North America; and that which we tread down as an insignificant weed in our European meadows is there reared with the most tender care in the botanical gardens. If we pass in review the vegetation of different countries, we see that causes appearing similar in our present knowledge of them bring forth indeed _similar_, but by no means the same, forms of plants. To the plants of a particular northern latitude correspond in the analogous height of the Alps, situated southward, other species of the same genera, or other genera of the same family; or the plants of America are represented in the same latitudes in the Old World by plants which are different, but closely allied, in their development. Nay, even plants which belong to totally different families assume, at least in their outward appearance, similar shapes. Thus the cactus plants of the New World correspond to the leafless, fleshy spurges of the torrid Africa.

If, again, we anticipate that a greater variety of conditions of vegetation is the cause why the variety of vegetation, the number of species of plants, continually augments from the pole toward the equator, and that on the same account the number of sociably growing plants, of species which clothe great tracts in countless individual specimens, also increases in the same measure, we find that we are still far from being enabled to give a scientific account of the matter. It seems to us wholly the result of caprice that particular plants are distributed widely over the globe, while others must live cribbed in the narrowest spot, as, for instance, the Wulfenia, occurring exclusively on the Carinthian Alps; that particular families, like the _Compositæ_, flourish abroad over the whole earth, while others, like the peppers and the palms, only occur between very definite degrees of latitude on either side of the equator, the _Proteaceæ_ only in the Southern Hemisphere, the cactus tribe only in the western half of our earth. Just as inexplicable is the _mode of distribution_ of the families of plants. While the palms diminish in number from the equator into higher latitudes, the _Compositæ_ attain their highest development in the zones of mean temperature, their number of species diminishes from these in both directions, equally toward the equator and toward the poles; while, finally, the grasses increase constantly from the equator toward the poles.

This, to us inexplicable, mode of distribution of plants according to species, genera, families, orders, and classes gives rise to certain peculiar regions on the globe, which are characterized by the predominance of certain forms of plants, or by the exclusive occurrence of particular families. These portions of the earth’s surface are called Geographical Regions of Plants, and to them have been applied the names of men who have made themselves especially famous by the investigation of these places.

I have already alluded to the regions of saxifrages and mosses, or Wahlenberg’s region, which extends from the eternal snow of the poles, or the summits of the mountains, down to the limit of the growth of trees, and is distinguished by the absence of arborescent plants, and even of the taller shrubs. Adjoining this comes the great Linnæan region, including northern Europe and northern Asia to the great chain of mountains which extends from the Pyrenees to the Alps. Woods of conifers, or deciduous trees, luxuriant meadows, and broad heaths, in Asia the peculiar salt steppes, especially determine the characters of this region, which, at least in its European portion, is now too widely taken possession of to exhibit its natural physiognomy. The wide basin from the Alps to Atlas, the deepest part filled by the Mediterranean Sea, forms a third region, distinguished by the abundance of aromatic Labiate plants, fair, but fleeting, lily plants, and the resinous rock-roses. The solitary dwarf-palm and balsam-trees denote in this, De Candolle’s region, the transition to the tropics. Parallel to the two last-named regions, North America is divided into a northern region named in honor of Michaux, distinguished by peculiar conifers, oaks and walnuts, by innumerable asters and golden-rods from the Linnæan region, and a southern, Pursh’s region, in which most strikingly appear the trees with broad shining leaves and large splendid flowers, like the tulip-tree, the magnolia, and others defining the character. Between Kämpfer’s region, comprehending China and Japan, Wallich’s in the highlands of India, and the Polynesian, or island region of Reinwardt, renowned for its poison-tree and its giant-flower, lies Roxburgh’s region, which extends through both the Indian peninsulas, which conceals among the shadows of the monster fig-trees the _Scitaminaceæ_, or aromatic lilies, like ginger, cardamums, and turmeric, or in little woods of aromatic barks, like the cinnamon and cassia, matures in thick, shapeless stems the starch of the sago. We pass over Blume’s region in the mountains of Java, Chamisso’s in the Archipelago of the South Sea, and Forster’s region in New Zealand, and turn again to Africa, where the desert, Delile’s region, ripens, in the oases, the date, and in the tender-leaved acacias concocts the abundance of gum-arabic and senega, which commerce brings to the service of our industry. To this, eastward, adjoins Forskäl’s region, where the balsam-trees predominate; on the south, Adanson’s, the characteristic plant of which perpetuates the name of that enlightened botanist, the thousand-yeared giant stem of the _Adansonia digitata_, the baobab, or monkey’s-bread. The little known Africa gives only one more region, at its southern extremity, Thunberg’s, bedecked with stapelias, mesembryanthemums, brilliant heaths, and evil-scented becku-shrubs, but poor in woods. New Holland and Van Diemen’s Land bear the name of their first and most profound botanical investigator, Robert Brown; and Central and South America distribute their vegetable riches into eight more regions, which are dedicated to Jacquin, Bonpland, Humboldt, Ruiz and Pavon, Swartz, Martius, St. Hilaire, and D’Urville; among these, Jacquin’s region is remarkable for its strange cacti; Humboldt’s, on the heights of the South American Andes, for its Quinoa forests; and that of Martius, in the interior of Brazil, for its abundance of palms, for its quantity of climbing plants or lianes and parasitic plants.

All over the globe has man, for the supply of necessary food, selected almost solely summer plants, that is, such plants as complete their whole vegetative processes, or, at all events, the development of all the parts containing nutrient matter, within the course of a few months. By this means he has rendered himself independent in the half-tropical regions of the evil action of the dry season, and in the higher latitudes of the destructive influence of cold, and thus ensured the possibility of cultivating plants, which there must be killed by the drought of summer, here by the cold of winter. Setting aside the cultivation of fruits, which serve rather pleasure than necessity, there remain but three arborescent vegetables in the whole world which can be included among the true food-plants, namely, the bread-fruit, the cocoanut, and the date, which actually furnish the chief proportion of the food of great bodies of men and over widely extended areas, and thence have become objects of culture; the _Cycadaceæ_, and sago-palms, on account of their starchy parenchyma, can at most perhaps be taken into our reckoning only in a very limited circle in the East Indies. All the rest of the food-plants are either such as possess a subterraneous, usually tuberous stem, which sends up shoots above the soil, persisting but a few months, on which develop flowers and fruit, while during the remaining time sleeping, as it were, beneath the protecting coverlet of earth, it sets the disfavor of the climate at defiance, or such as die during or at the end of a short period of vegetation, and ensure the future reproduction in the slumbering germ of the seed. To the former belong, for instance, the potato, derived from the Cordilleras of Chili, Peru, and Mexico; to the latter, almost all our corn-plants.

One plant alone distinguishes itself among the cultivated plants by a peculiar mode of vegetation, a plant which was perhaps the earliest gift of Nature to man awakening to life, and thus the object of the earliest culture; I mean the banana. And this plant was not merely the first, but the most valuable gift of Nature; its slightly aromatic, sweet and nutritive fruits are the sole, or at least the chief, food of the major part of the inhabitants of the hotter regions. A creeping subterraneous root-stock sends out on high, from lateral buds, a shaft fifteen to twenty feet long, which consists merely of the rolled-up, sheath-like leaf-stalks, bearing the velvet-like glancing leaves, often ten feet long and two feet broad; the midrib of the leaf alone is firm and thick, but the blade of the leaf on either side so delicate that it is readily torn by the wind, whence the leaf acquires a peculiar feathered aspect. Among the leaves presses up the rich cluster of flowers, which within three months after the shoot has arisen forms from 150 to 180 ripe fruits, about the size and form of a cucumber. The fruits weigh altogether about 70 or 80 pounds, and the same space which will bear 1,000 pounds of potatoes brings forth in a much shorter time 44,000 bananas; and if we take account of the nutritious matter which this fruit contains, a surface which, sown with wheat, feeds one man, planted with bananas, affords sustenance to five-and-twenty. Nothing strikes the European landing in a tropical country so much as the little spot of cultivated land round a hut, which shelters a very numerous Indian family.

Not till long after did man learn to know and cultivate the gifts of Ceres. It must, in fact, surprise us, at present, to see that but a few species of a single family of plants furnish the principal food of the greater proportion of mankind, namely, the so-called corn-plants, or _Cerealia_, of the family of grasses. This family includes nearly 4,000 species, and yet not twenty of them are cultivated for the food of man. In their real nature these cultivated grasses are all summer plants, but varieties have been obtained from some of the most important of them, which, in the proper climate, sown in autumn, germinate and pass the winter under the warm covering of snow, so that they are in a condition to shoot out strongly in the spring, while the soil is being prepared for the other summer plants.

Barley has the widest range of distribution of all the _Cerealia_, and is cultivated from the extreme limits of culture in Lapland to the heights immediately beneath the equator. But it has by no means the same importance everywhere that it has in the northern region, where, in a little narrow zone, it appears as the sole bread-corn. In Lapland and northern Asia, rye soon appears beside it, but by the inclemency of the climate confined to favorable years, and therefore not properly to be regarded as the principal food. First in Norway, Sweden, Finland, and Russia does the rye become the peculiar bread-corn; and wheat takes its place beside it in the north of Great Britain and Germany, as the rye before joined barley. In the centre of Germany, in the south of Great Britain, in France, and in a wide range toward the East, including the whole of the Caspian Sea, wheat is the prevailing cultivated plant, which in the basin of the Mediterranean and throughout North America is associated with maize. Rice takes the place of the latter in Egypt and in northern India, and holds undisputed rule in the peninsulas of India, in China, Japan, and the East Indian islands, shares it in the west coast of Africa with maize, which, on the other hand, is the exclusively cultivated corn-plant of the greatest part of tropical America, with only some unimportant exceptions. In southern America, Africa, and Australia wheat again enters the field with the decreasing temperature. The culture of _Tef_ and _Tocusso_ in Abyssinia, of millet in Western Africa and Arabia, as well as of _Eleusine_ and millet in the East Indies, are quite of subordinate importance.

Some other plants bear a far more important share in the nutrition of mankind than the grasses last named. Even in the most northern zone of the barley and rye, the buckwheat is an object of tolerably extensive culture. With the already named banana, the yams, the manioc, and the batatas contribute largely to the daily food of the inhabitants of the tropics, of the Old as of the New World, added to which the Andes presents itself a peculiar vegetable, the quinoa, a plant which simultaneously produces edible tubers and abundance of seeds, comparable to those of buckwheat. Lastly, we may not pass over the _Bread-fruit_, in the proper sense of the word, which is the principal food of the inhabitants of the large islands which extend from the East Indies through the whole tropical ocean to the west coast of America, the gift of a large and beautiful tree of the family of the nettle, which from the use it is turned to is called the bread-fruit tree. For the sake of variety, some also cultivate with it the tarroo-root, the _Tacca_ tubers, or some ferns, the farinaceous leaf-stalks of which afford a dainty meal. Last of all I will mention the potato, which has spread over the whole earth with such rapidity from the mountains of the New World that in many places it threatens, not exactly to the advantage of mankind, to supplant every other culture.

PHYSIOGNOMY OF PLANTS
--ALEXANDER VON HUMBOLDT

The carpet of flowers and of verdure spread over the naked crust of our planet is unequally woven; it is thicker where the sun rises high in the ever cloudless heavens and thinner toward the poles, in the less happy climes where returning frosts often destroy the opening buds of spring or the ripening fruits of autumn. Everywhere, however, man finds some plants to minister to his support and enjoyment.

Lichens form the first covering of the naked rock, where afterward lofty forest trees rear their airy summits. The successive growth of mosses, grasses, herbaceous plants and shrubs or bushes, occupies the intervening period of long but undetermined duration. The part which lichens and mosses perform in the northern countries is effected within the tropics by Portulacas Gomphrenas and other low and succulent shore-plants. The history of the vegetable covering of our planet, and its gradual propagation over the desert crust of the earth, has its epochs as well as that of the migrations of the animal world.

When leaving our oak forests, we traverse the Alps or Pyrenees, and enter Italy or Spain, or when we direct our attention to some of the African shores of the Mediterranean, we might easily be led to draw the erroneous inference that hot countries are marked by the absence of trees. But those who do so, forget that the south of Europe wore a different aspect on the first arrival of Pelasgian or Carthaginian colonies; they forget that an ancient civilization causes the forests to recede more and more, and that the wants and restless activity of large communities of men gradually despoil the face of the earth of the refreshing shades which still rejoice the eye in northern and middle Europe, and which even more than any historic documents prove the recent date and youthful age of our civilization.

The deserts to the south of the Atlas, and the immense plains or steppes of South America, must be regarded as only local phenomena. The latter, the South American steppes, are clothed, in the rainy season at least, with grass and with low-growing, almost herbaceous, mimosas. The African deserts are, indeed, at all seasons, devoid of vegetation; seas of sand, surrounded by forest shores clothed with perpetual verdure. A few scattered fan-palms alone recall to the wanderer’s recollection that these awful solitudes belong to the domain of the same animated terrestrial creation which is elsewhere so rich and so varied. The fantastic play of the mirage, occasioned by the effects of radiant heat, sometimes causes these palm trees to appear divided from the ground and hovering above its surface, and sometimes shows their inverted image reflected in strata of air undulating like the waves of the sea. On the west of the great Peruvian chain of the Andes, on the coasts of the Pacific, I have passed entire weeks in traversing similar deserts destitute of water.

When once a region has lost the covering of plants with which it was invested, if the sands are loose and mobile and are destitute of springs, and if the heated atmosphere, forming constantly ascending currents, prevents precipitation taking place from clouds, thousands of years may elapse ere organic life can pass from the verdant shores to the interior of the sandy sea, and repossess itself of the domain from which it had been banished.

Those, therefore, who can view nature with a comprehensive glance and apart from local phenomena, may see from the poles to the equator organic life and vigor gradually augment with the augmentation of vivifying heat. But, in the course of this progressive increase, there are reserved to each zone its own peculiar beauties; to the tropics, variety and grandeur of vegetable forms; to the north, the aspect of its meadows and green pastures, and the periodic reawakening of nature at the first breath of the mild air of spring. Each zone, besides its own peculiar advantages, has its own distinctive character.

In determining leading forms, or types, on the individual beauty, the distribution, and the grouping of which the physiognomy of the vegetation of a country depends, we must not follow the march of systems of botany, in which from other motives the parts chiefly regarded are the smaller organs of propagation, the flowers and the fruit; we must, on the contrary, consider solely that which by its mass stamps a peculiar character on the total impression produced, or on the aspect of the country. Among the leading forms of vegetation to which I allude, there are, indeed, some which coincide with families belonging to the “natural systems” of botanists.

Such are the forms of bananas, palms, Casuarinæ, and Coniferæ. But the botanic system divides many groups which the physiognomist is obliged to unite.

1, Myrtle; 2, Myrrh; 3, Hemlock; 4, Wormwood; 5, Frankincense; 6, Hyssop]

We will begin with the palms, the loftiest and noblest of all vegetable forms, that to which the prize of beauty has been assigned by the concurrent voice of nations in all ages; for the earliest civilization of mankind belonged to countries bordering on the region of palms, and to parts of Asia where they abound. Their lofty, slender, ringed, and, in some cases, prickly stems terminate in aspiring and shining either fan-like or pinnated foliage. The leaves are frequently curled, like those of some Gramineæ. Smooth, polished stems of palms carefully measured by me had attained 192 English feet in height. In receding from the equator and approaching the temperate zone, palms diminish in height and beauty. The indigenous vegetation of Europe only comprises a single representative of this form of plants, the sea-coast dwarf-palm or Chamærops, which in Spain and Italy extends as far north as the 44th parallel of latitude. The true climate of palms has a mean annual temperature of 78°.2-81°.5 Fahr. The date, which is much inferior in beauty to several other genera, has been brought from Africa to the south of Europe, where it lives, but can scarcely be said to flourish, in a mean temperature not exceeding 59°-62°.4 Fahr.

In all parts of the globe the palm form is accompanied by that of plantains or bananas; the Scitamineæ and Musaceæ of botanists, Heliconia, Amomum, and Strelitzia. In this form, the stems, which are low, succulent, and almost herbaceous, are surmounted by long, silky, delicately veined leaves of a thin, loose texture, and bright and beautiful verdure. Groves of plantains and bananas form the ornament of moist places in the equatorial regions.

The form of Malvaceæ and Bombaceæ, represented by Ceiba, Cavanillesia, and the Mexican hand-tree Cheirostemon, has enormously thick trunks; large, soft, woolly leaves, either heart-shaped or indented; and superb flowers, frequently of a purple or crimson hue. It is to this group of plants that the baobab, or monkey bread-tree (Adansonia digitata), belongs, which, with a very moderate elevation, has a diameter of 32 English feet, and is probably the largest and most ancient organic monument on our planet. In Italy the Malvaceæ already begin to impart to the vegetation a peculiar southern character.

The delicately pinnated foliage of the Mimosa form, of which Acacia, Desmanthus, Gleditschia, Porleria, and Tamarindus are important members, is entirely wanting in our temperate zone in the Old Continent, though found in the United States, where, in corresponding latitudes, vegetation is more varied and vigorous than in Europe. The umbrella-like arrangement of the branches, resembling that seen in the stone-pine in Italy, is very frequent among the Mimosas. The deep blue of the tropic sky seen through their finely divided foliage has an extremely picturesque effect.

The heath form belongs more especially to the African continent and islands. Arborescent heaths, like some other African plants, extend to the northern shores of the Mediterranean; they adorn Italy and the cistus-covered grounds of the south of Spain. In the countries adjoining the Baltic, and further to the north, the aspect of this form of plants is unwelcome as announcing sterility.

The cactus form is almost exclusively American. Sometimes spherical, sometimes articulated or jointed, and sometimes assuming the shape of tall, upright polygonal columns resembling the pipes of an organ, this group presents the most striking contrast to those of Liliaceæ and bananas.

While the above-mentioned plants flourish in deserts almost devoid of vegetation, the Orchideæ enliven the clefts of the wildest rocks and the trunks of tropical trees blackened by excess of heat. This form (to which the vanilla belongs) is distinguished by its bright green succulent leaves, and by its flowers of many colors and strange and curious shape, sometimes resembling that of winged insects, and sometimes that of the birds which are attracted by the perfume of the honey vessels. Such is their number and variety that, to mention only a limited district, the entire life of a painter would be too short for the delineation of all the magnificent Orchideæ which adorn the recesses of the deep valleys of the Andes of Peru.

The Casuarina form, leafless, like almost all species of cactus, consists of trees with branches resembling the stalks of our Equisetums. It is found only in the islands of the Pacific and in India, but traces of the same singular rather than beautiful type are seen in other parts of the world.

As the banana form shows the greatest expansion, so the greatest contraction of foliage is shown in Casuarinas, and in the form of needle-trees (Coniferæ). Pines, thuias, and cypresses belong to this form, which prevails in northern regions, and is comparatively rare within the tropics: in Dammara and Salisburia the leaves, though they may still be termed needle-shaped, are broader. In the colder latitudes, the never-failing verdure of this form of trees cheers the desolate winter landscape, and tells to the inhabitants of those regions that when snow and ice cover the ground the inward life of plants, like the Promethean fire, is never extinct upon our planet.

Like mosses and lichens in our latitudes, and like Orchideæ in the tropical zone, plants of the Pothos form clothe parasitically the trunks of aged and decaying forest trees: succulent herbaceous stalks support large leaves, sometimes sagittate, sometimes either digitate or elongate, but always with thick veins. The flowers of the Aroideæ are cased in hooded spathes or sheaths, and in some of them when they expand a sensible increase of vital heat is perceived. Stemless, they put forth aerial roots. Pothos, Dracontium, Caladium, and Arum all belong to this form, which prevails chiefly in the tropical world. On the Spanish and Italian shores of the Mediterranean, Arums combine with the succulent Tussilago, the acanthus, and thistles, which are almost arborescent, to indicate the increasing luxuriance of southern vegetation.

Next to the last-mentioned form, of which the Pothos and Arum are representatives, I place a form with which, in the hottest parts of South America, it is frequently associated--that of the tropical twining rope-plants, or Lianes, which display in those regions, in Paullinias, Banisterias, Bignonias, and Passifloras, the utmost vigor of vegetation. It is represented to us in the temperate latitudes by our twining hops and by our grapevines. On the banks of the Orinoco the leafless branches of the Bauhinias are often between 40 and 50 feet long; sometimes they hang down perpendicularly from the high top of the Swietenia, and sometimes they are stretched obliquely like the cordage of a ship; the tiger-cats climb up and descend by them with wonderful agility.

In strong contrast with the extreme flexibility and fresh, light-colored verdure of the climbing plants, of which we have just been speaking, are the rigid, self-supporting growth and bluish hue of the form of the Aloes, which, instead of plaint stems and branches of enormous length, are either without stems altogether or have branchless stems. The leaves, which are succulent, thick, and fleshy, and terminate in long points, radiate from a centre and form a closely crowded tuft. The tall-stemmed aloes are not found in close clusters or thickets like other social or gregarious plants or trees; they stand singly in arid plains, and impart thereby to the tropical regions in which they are found a peculiar, melancholy, and I would almost venture to call it, African character. Taking for our guides resemblance in physiognomy, and influence on the impression produced by the landscape, we place together under the head of the Aloe form (from among the Bromeliaceæ), the Pitcairnias, which in the chain of the Andes grow out of clefts in the rocks; the great Pourretia pyramidata (the Atschupalla of the elevated plains of New Granada); the American Aloe (Agave); Bromelia aranas and Bromelia karatas; from among the Euphorbiaceæ the rare species which have thick, short candelabra-like divided stems; from the family of Asphodeleæ the African Aloe and the Dragon tree (Dracæna draco); and lastly, from among the Liliaceæ, the tall, flowering Yucca.

If the Aloe form is characterized by an almost mournful repose and immobility, the form of Gramineæ, especially the physiognomy of arborescent grasses, is characterized, on the contrary, by an expression of cheerfulness and of airy grace and tremulous lightness, combined with lofty stature. Both in the East and West Indies groves of bamboo form shaded overarching walks or avenues. The smooth, polished and often lightly waving and bending stems of these tropical grasses are taller than our alders and oaks. The form of Gramineæ begins even in Italy, in the Arundo donax, to rise from the ground and to determine by height as well as mass the natural character and aspect of the country.

The form of ferns, as well as that of grasses, becomes ennobled in the hotter parts of the globe. Arborescent ferns, when they reach a height of above forty feet, have something of a palm-like appearance; but their stems are less slender, shorter, and more rough and scaly than those of palms. Their foliage is more delicate, of a thinner and more transparent texture, and the minutely indented margins of the fronds are finely and sharply cut. Tree ferns belong almost entirely to the tropical zone, but in that zone they seek by preference the more tempered heat of a moderate elevation above the level of the sea, and mountains two or three thousand feet high may be regarded as their principal seat. In South America the arborescent ferns are usually associated with the tree which has conferred such benefits on mankind by its fever-healing bark. Both indicate by their presence the happy region where reigns a soft, perpetual spring.

I will next name the form of Liliaceous plants (Amaryllis, Ixia, Gladiolus, Pancratium), with their flag-like leaves and superb blossoms, of which southern Africa is the principal country; also the willow form, which is indigenous in all parts of the globe, and is represented in the elevated plains of Quito (not in the shape of the leaves, but in that of the ramification), by Schinus Molle; Mytraceæ (Metrosideros, Eucalyptus, Escallonia myrtilloides); Melastomaceæ, and the laurel form.

It is under the burning rays of a tropical sun that vegetation displays its most majestic forms. In the cold north the bark of trees is covered with lichens and mosses, while between the tropics the Cymbidium and fragrant vanilla enliven the trunks of the Anacardia and of the gigantic fig-trees. The fresh verdure of the Pothos leaves and of the Dracontia contrasts with the many colored flowers of the Orchideæ; Climbing Bauhinias, Passifloras, and yellow flowering Banisterias twine round the trunks of the forest trees. Delicate blossoms spring from the roots of the Theobroma, and from the thick and rough bark of the Crescentias and the Gustavia. In the midst of this profusion of flowers and fruits, and in the luxuriant intertwinings of the climbing plants, the naturalist often finds it difficult to discover to which stem the different leaves and flowers really belong. A single tree adorned with Paullinias, Bignonias, and Dendrobium forms a group of plants which, if disentangled and separated, would cover a considerable space of ground.

In the tropics vegetation is generally of a fresher verdure, more luxuriant and succulent, and adorned with larger and more shining leaves than in our northern climates. The “social” plants, which often impart so uniform and monotonous a character to European countries, are almost entirely absent in the equatorial regions. Trees almost as lofty as our oaks are adorned with flowers as large and as beautiful as our lilies. On the shady banks of the Rio Magdalena in South America, there grows a climbing Aristolochia bearing flowers four feet in circumference which the Indian boys draw over their heads in sport, and wear as hats or helmets. In the islands of the Indian Archipelago the flower of the Rafflesia is nearly three feet in diameter, and weighs above fourteen pounds.

THE GENESIS OF FLOWERS
--ALEXANDER S. WILSON

The flowers most generally known are brightly colored flowers adapted for insect fertilization; only these require to attract insects, which is the end served by the perfume and conspicuous coloring. Very many plants, however, bear blossoms so small and obscurely colored that they are either entirely overlooked or not reckoned as flowers at all. The wind-fertilized flowers of the dock and nettle have no occasion for the services of insects, and are destitute of honey, odor, and brilliant petals. Still more insignificant in appearance are the little self-fertilizing cleistogamic flowers, which, toward the end of the season, are produced on the dog-violet. All three kinds possess stamens and pistils, and are therefore recognized as flowers by botanists. Besides stamens and pistils, which are the essential organs of a flower, petals and sepals are usually present. The petals collectively compose the corolla, the sepals the calyx; both together being spoken of as the floral envelopes or perianth. Occasionally, as in the ash, the flower is reduced to its essential organs, the floral envelopes being absent. Plants bearing flowers, whether with or without floral envelopes, are designated phanerogams or flowering plants; they constitute the highest division of the vegetable kingdom. Ferns and mosses, again, are examples of the cryptogamic or flowerless class; they never bear flowers or seeds, but are propagated by minute reproductive bodies termed spores. This class is divided into thallophytes and vascular cryptogams. The organization of a thallophyte is very simple; the plant body of a fungus or sea-weed, for example, consists entirely of similar cells, and externally shows no distinction into root, stem, and leaf. The structure of a vascular cryptogam, such as a club-moss, horsetail, or fern, is more complicated; both cells and vessels enter into the composition of its tissues, and externally the distinction of stem and leaf is apparent. Phanerogams also admit of a twofold division into gymnosperms and angiosperms; conifers, cycads, and yews are gymnospermous, having naked seeds, exposed either on the ends of branches or on the surface of open scales. All ordinary flowering plants produce their seed in the interior of a closed, ovary, as the lower part of the pistil is called; from this peculiarity they are termed angiosperms.

Only the remains of thallophytes have hitherto been discovered in the oldest Palæozoic rocks. Vascular cryptogams appear in the Silurian strata, attain their maximum in the Carboniferous age, and in succeeding formations are gradually displaced by gymnosperms. The latter occur as early as the Devonian period, but the prevailing type of vegetation down to the close of Palæozoic time continued to be cryptogamic. Angiosperms possibly existed as far back as the Permian times, but it is only in the chalk that their remains begin to be abundant; the vast majority of Mesozoic plants seem to have belonged to the gymnospermous type. Plants with conspicuous flowers only date from Tertiary times; they increase in number and importance as we approach the present day.

Although the plants entombed in the rocks are only an inconsiderable fraction of the numbers that formerly existed, the general succession just indicated is fully made out, and as the palæontological evidence accumulates it tends more and more to establish the view that colored blossoms are, geologically speaking, of comparatively recent origin. The vegetation of the earlier geological epochs was marked by a singular uniformity of character; not only were there fewer species than now, and these widely distributed over the globe, but the monotonous green of Palæozoic and Mesozoic forests was unrelieved by gay blossoms such as adorn our fields and orchards. We are indebted to geology for another important fact; fossil plants occur which have no near relatives in the existing flora. Intermediate forms which can not properly be classified with any living family are met with; in others the characters of several modern groups are blended. Although these generalized forms rather upset our systems of classification, they have an important bearing on the origin of living plants. But what a different aspect, when the coal plants were growing in primeval luxuriance, the landscape must have worn from that on which we are accustomed to look! Odd, uncouth lepidodendra of arborescent growth, huge reed-like calamites, gigantic ferns stretched in interminable forests, clothed in one unvaried tint of sombre green. How different is the scene which nature now presents!--mountains glowing with the purple bloom of heather; hillsides where the furze has spread its cloth of gold; meadows bright with daisies, ranunculi, and cuckoo-flowers; banks where the wild thyme and bluebell grow! The contrast affords a hint of the transformation in our world effected by the introduction of flowers.

Our knowledge may not enable us to describe all the minute steps which led to this remarkable change, but we can at least indicate with great probability the nature of the process and some of the agencies which contributed to bring about this result. To suppose that each species of plant was independently created as we now see it, implies not one creation merely, but many successive creations; moreover, it leaves unexplained all the curious affinities which exist among the members of the vegetable kingdom. The gradations of structure, the geological succession, and the peculiarities of plant growth are much more intelligible when we view the plants which now inhabit the earth as the lineal descendants of those which lived during the earlier ages of geology. From the nature of the case, the theory of development does not admit of actual demonstration; still the evidence in support of it is such that its advocates are entitled to claim a verdict on the mass of indirect and circumstantial evidence.

Among palæozoic cryptogams, we have evidence of the existence of structures which, with comparatively little modification, might be converted into what we now regard as flowers. The abundant remains of lepidodendra in the Coal-measures testify to the important place attained by the group of lycopods, or club mosses, in the Palæozoic flora. To this family might very well have belonged the archetype from which our modern blossom-bearing plants have come. Our knowledge of this group is derived both from fossil remains and from forms still extant. The selaginellas, so commonly cultivated in greenhouses, are examples; also the little club moss (Lycopodium selaginodes) of our highland moors. The last mentioned, though a diminutive form, possesses special interest, being one of the vascular cryptogams which produce two kinds of spores. This heterosporous character was, however, a common feature of extinct lycopods; both large and small spores have been detected in great numbers in coal.