floating geiins of vegetation, ■which soon clothe the rough rock with verdure of a 

 humbler kind, and ultimately, by the growth and decay of successive generations, 

 form a soil for the sustenance of the higher foi-ms of vegetable life. 



d. Another important requisite os moistm-e. But the arid sands of the great 

 African desert are not absolutely destitute of vegetable life. Even there, certain 

 species of Stapelia are said to flourisli, and those dreary regions, where neitlier rain 

 nor dew ever falls, are occasionally enlivened by spots of verdiu-e, like islands in 

 the ocean, composed of these and kindred plants. 



e. Extremes of heat are not always fatal to vegetation. In one of the Geysers 

 of Icelandj which was hot enough to boil an egg in four minutes, a species of 

 Cjiara lias been found, in a gro^ving and fruitful state. A hot spring at the 

 Island of Luzon, which raises the theiTnometer to 187°, has plants growing in it 

 and on its borders. But the most exti-aordinary case of all, is one recorded by 

 Sir J. Staunton, '^t the Island of Amsterdam a spring was found, tlie mud of 

 which, far hotter than boUing water, gave birth to a species of liverwort.' Other 

 suiiOar instances are on record.) 



/. Nor are the extremes of cold fatal to eveiy form of vegetation. The rein-, 

 deer lichen, of Lapland,;^rows in vast quantities among almost perpetual snows. 

 And far in the arctic regions, the eternal snows are often reddened, for miles in 

 extent, by a minute vegetal)le of the Alga; tribe, called red snow, of a structm-e 

 the simj)lest that has yet been observed, consisting of a single round cell contain- 

 ing a fluid. 



g. Light is also a liighly important agent in vegetation ; yet there are plants 

 capable of flourishing in situations where it would seem that no ray of it ever 

 entered^.' Mushrooms, and even plants of higher orders, have been found growing 

 amidst the perpetual midnight of deep caverns and mines. Sea weeds of a bright 

 green color have been drawn up from the bed of the ocean, from depths of moi-e 

 than 100 fathoms. 



13. The vegetable kingdom (.is no less remarkable for its rick 

 and boundless variety, than for its wide diffusion, (jp'lants differ 

 from each other in respect to fonn, size, color, habits, structnre, 

 and properties, to an unlimited degree, so that it would be diffi- 

 cult, indeed, to find two individuals, even of the same species, 

 wliich should perfectly coincide in all these points.) 



a. Yet this variety is never abrupt, never capricious; but here, as in other 

 departments of nature, uniform resemblancee are so blended with it, as to lay an 

 adequate foundation for Systematic Botany. 



14. Tlae same causes which affect the general increase of 

 plants, exercise, also, an important influence in determining then- 

 character. Hence, every chmatei'has not only its own pecidiar 

 degree of vegetable activity, but also its peculiar species.) 



a. Other causes, besides temperature, are eflacient in determining the species of 



