'.. ; t^o e ; - iM^it^L- 



GEOGRAPHICAL- DISTRIBUTION OF PLANTS. 



BY L. WETHERELL. 



The above illustration is from "Rodgers's Scien- 

 tific Agriculture;'' and was designed by the author 

 to aid the mind in acquiring a knowledge of the dis- 

 tribution of plants with regard to height; to show 

 the latitude of prevailing winds, and the altitude of 

 no rain and of almost constant rain. The figures 

 on the right hand side of the cut, denote the degrees 

 of north latitude; those on the left denote the height 

 of mountains, graduated in miles. There is also an 

 attempt to show the lines which separate between 

 the elevation of the different species of plants; " and 

 the line of perpetual snow." 



It is a well established fact that a greater degree 

 of cold prevails in the upper regions of the atmos- 

 phere than at low levels. This is manifest from the 

 fact, that, the mountains of the equatorial region at 

 the height of 16,000 feet are covered with perpetual 

 snow; the height of the snow line diminishes in 

 passing from the equator to the poles of the earth, 

 until it rests on the sea 'level at 70 or 80 degrees 

 north latitude; this is true of the summer tempera- 

 ture: the snow line is much further south when the 

 sun is in the tropic of Capricorn. According to 

 Prof. Leslie, the mercury in the thermometer falls 



for every 30u ,■ . fa - i . 

 e an elevation of 1-5,00 i feel ■ ■ ar 

 the equator produces the sa 

 the vegetable kingdom as the <ii. tancs : 

 miles north of the equator on the 

 level of the sea. An elevation of 7,000 

 f. el in the tropics gives a temperature the 

 same as that of France, which is 49 de- 

 gr north latitude. 



, Humboldt, in his travels in S. America, 

 hag given a sketch of the vegetation of 

 the Andes, commencing in the torrid zone 

 on the level of the ocean, and ascending 

 to the region of " eternal snow." A con- 

 densed view of this sketch with the aid 

 of the cut, will enable the reader to gain 

 a very correct idea of the distribution of 

 plants, — remembering always that altitude 

 from the level of the s< a produces the 

 same effect upon climate and plants as 

 travelling north or south of the equator. 



1. The Tropical Zone. This is called 

 the region of palms, and extends from 

 the level of the sea to 3,500 feet. Here 

 grow in perfection the splendid palm fam- 

 ily, the sugar-cane, the coffee plant, the 

 tea plant, the orange, the lemon, the fig, 

 the citron, the pine-apple and the banana; 

 also the region of the nutmeg, cinnamon, 

 clove; and of the .various fragrant and 

 medicinal gums. Here are found, also, 

 various and valuable kinds of wood, as 

 the mahogany, the iron-wood, the teak- 

 tree, and the bread-fruit-tree; the various 

 kinds of dye-wood, as logwood, camwood, 

 Sic, Wheat does not flourish at this alti- 

 tude: maize, rice ami millet do — : these 

 with the bread-fruit, ! >. cassava, 

 manioc roots, taro-root and the yam, fur- 

 nish food for more than one-third of the 

 human race. 



2. The Temperate Zone. This re- 

 gion p.^v._. in great abundance the 



grains from which man's bread is made. Here the 

 wine-grape is cultivated in the greatest perfection; 

 also the apple, pear, plum, peach, cherry, apricot, &c. 

 Some of them flourish better in the northern and 

 others in the southern part of this region, or what 

 corresponds thereto, the less or greater altitude. 



3. Arctic Zone. In passing from the temperate 

 to the arctic zone, the limit of the vegetable world 

 is soon found: very few plants are seen above the 

 elevation of fourteen thousand feet. Lichens arc 

 the first that appear on the outside of the vegeta- 

 ble world, whether altitude or latitude he regarded. 

 More than 2,400 species are known. As you ap- 

 proach the limits of the temperate zone, shrubs and 

 herbaceous plants appear — then the evergreens, min- 

 gled with the birch and willow. Wheat scarcely 

 comes to maturity — some of the more common gar- 

 den vegetables are produced here at an altitude cor- 

 responding to the temperature of between 60 and 

 70 degrees north latitude. 



The'dwarf birch and willow are the trees nearest the 

 snow region : the former seldom exceeds two feet in 

 height, and the latter is still smaller. The reindeer 

 moss grows beyond this limit, proceeding north. As 

 you approach the equator from the region of the 

 dwarf birch, the common birch, the mountain asl . 



