VEGETABLES VEGETATION. 



793 



derived from the sulphur, air and water, with which 

 the plants were supplied. If the latter opinion be 

 adopted, we must infer either that the vital prin- 

 ciple, which certainly controls chemical affinity in 

 a surprising manner, and directs this power in the 

 production of new compounds from elementary 

 bodies, may likewise convert one element into 

 another ; or that some of the substances supposed 

 by chemists to be simple, such as oxygen and hy- 

 drogen, are compounds, not of two, but of a variety, 

 of different principles. But as these conjectures 

 are at variance with the facts and principles of 

 chemistry, it would appear that some error must 

 have been committed in the experiments. For 

 an account of the spontaneous changes to which 

 vegetables are liable, see the article on Fermenta- 

 tion ; see also the article Plants. 



VEGETABLES. See Plants. 



VEGETATION. The wide extension of vege- 

 table life furnishes one of the most striking exam- 

 ples of the productive power of nature. Every 

 climate has its peculiar vegetation. The coldest 

 countries are not entirely destitute of it, and it has 

 been thought by naturalists that even perpetual 

 snow is the abode of some species of vegetables. 

 Saussure discovered in it a reddish dust, and the 

 navigators in the arctic regions frequently observed 

 in it a red colouring matter, supposed to belong to 

 the order algce. The absence of light does not al- 

 together prevent vegetable existence. Caverns 

 and mines produce certain plants, principally those 

 of the cryptogamous class. Vast fields of marine 

 plants spring from the depths of the ocean, espe- 

 cially towards and within the tropics. The vine- 

 leaved fucus vegetates at the depth of two hundred 

 feet. The surface of the Atlantic, in some parts, 

 is covered with masses of floating fuci, which are 

 supposed by botanists to grow at the bottom of the 

 sea, and to be torn off when ripe by the motion of 

 the waters. Extreme heat is not destructive of 

 vegetation, provided it be accompanied by humidity. 

 Plants grow not only on the borders, but even in 

 the waters, of hot springs. The greatest obstacle 

 to vegetation is the absence of moisture. Those 

 sandy tracts where rain seldom or never falls, and 

 where the soil is constantly shifted about by the 

 winds, exhibit a complete sterility. The chemical 

 nature of the soil influences the size and vigour of 

 plants, rather than sets limits to their cultivation : 

 common salt, however, dissolved and scattered over 

 the earth, almost entirely prevents their growth. 

 The scale of atmospherical heat is what ordinarily 

 determines the character and progress of vegetation. 

 In the torrid zone, therefore, it is only necessary 

 to ascend mountains to a certain height, to find 

 the trees, fruits and flowers of the temperate 

 zone, and, still higher, those of the frigid zone. 

 (See Mountains, and Temperature.) The vegeta- 

 tion which covers the sides of mountains, thus 

 forms distinct zones or bands, each having its pecu- 

 liar vegetable tribes. On the volcano of Teneriffe, 

 for example, five of these zones have been distin- 

 guished: 1. the region of vines; 2. of laurels; 3. 

 of pines; 4. of the alpine broom; and, 5. of grasses. 

 In the equinoctial regions, where the seasons differ 

 little in respect of heat, the geographical distribu- 

 tion of plants is regulated almost entirely by the 

 mean temperature of the whole year ; but, in the 

 temperate zone, this distribution depends more 

 upon the mean temperature of the summer season. 

 Some plants only require a certain degree of heat 

 for a short period, while for others a more moderate 



heat is sufficient, if of longer duration. Thus the 

 birch does not put forth leaves under a temperature 

 of 53 or 54 ; but the pine requires a long rather 

 than a warm summer. In Lapland, therefore, 

 where the summer, though short, is warm, the birch 

 rises nearer the line of perpetual congelation than 

 the pine ; but in the Alps and other high chains in 

 low latitudes, where the summer is longer, but 

 colder, the pine is seen after the birch has disap- 

 peared. 



The frigid zone contains but few species of 

 plants ; yet of these the vegetation in summer Is 

 extremely rapid. The verdure of countries within 

 the polar circle is confined chiefly to southern as- 

 pects, and the trees are of diminutive growth. 

 Besides mosses and lichens, there exist ferns, creep- 

 ing plants, and some shrubs yielding berries. In 

 the high latitudes of the northern temperate zone 

 are the pine and the fir, which show their adapta- 

 tion to a cold climate, by retaining their verdure 

 through the rigours of winter. Advancing south- 

 ward, we meet successively the oak, the elm, the 

 beech, the lime, and other forest trees. Several 

 fruit-trees, amongst which are the apple, the pear, 

 the cherry, and the plum, grow better in the 

 northern half of this zone ; while to its more southern 

 parts especially belong the more delicate fruits, 

 such as the olive, the lemon, the orange and the fig, 

 and, amongst trees, the cedar, the cypress and the 

 cork. The space comprised between the thirtieth 

 and the fiftieth parallels of latitude may be con- 

 sidered as the country of the vine and the mulberry. 

 Wheat extends as far north as the sixtieth degree; 

 oats and barley a few degrees farther. In the 

 southern part of this zone, maize and rice are more 

 commonly cultivated. The vegetation of the tor- 

 rid zone is characterized by a wealth, variety and 

 magnificence no where to be found in the other 

 regions of the globe. Under the beams of a tropi- 

 cal sun, the most juicy fruits and the most powerful 

 aromatics arrive at perfection ; the ground there 

 yields the sugar-cane, the coffee-tree, the palm, the 

 bread-tree, the pisang, the baobab, the date, the 

 cocoa, the vanilla, the cinnamon, the nutmeg, the 

 pepper, the camphor-tree, &c. The cow-tree of 

 South America yields vegetable milk. There are 

 also various sorts of dye-wood, and several species 

 of corn, peculiar to hot climates ; while the eleva- 

 ted tracts of these regions produce the plants of the 

 temperate countries. The vegetable forms near 

 the equator are in general more majestic, and their 

 colouring more brilliant, than in higher latitudes. 

 The largest trees are adorned with flowers, larger, 

 more beautiful, and more odoriferous, than those 

 of herbaceous plants in our zone. 



The distribution of plants cannot be explained 

 solely by the influence of climate, or by the 

 distribution of temperature; for it frequently 

 happens, that similar climates are found in dif- 

 ferent parts of the globe, without identity of 

 production. The climate of the high mountains 

 of the torrid zone is analogous to that of the tem- 

 perate zone ; yet Humboldt did not discover one 

 indigenous rose-tree in all South America; and 

 this shrub is entirety wanting in the southern 

 hemisphere. The genus erica (heath) is peculiar 

 to the old world, not one of the 137 species 

 known being found in the new. On the other 

 hand, the cactus (Indian fig) is confined to the new 

 world. According to Humboldt, the species of 

 plants at present known amount to 44,000. Of 

 these, 6000 are cryptogamous. The remaining 38,000 



