THE DIFFUSION OF VEGETATION. 15 



nitely, but no one of the fragments, alone, will still be a complete 

 plant. 



11. Animals, like plants, are organized bodies, endowed with 

 vitality, and composed of distinct parts, no one of which is com- 

 plete in itself; but they are raised above either plants or min- 

 erals, by the power of perception. 



a. These distinctions, long since suggested by the immortal Linnaeus, are per- 

 fectly obvious and definite, in the higher grades of the animal and vegetable 

 kingdoms ; but, in descending the scale, we recognize a gradual and constant 

 approach, ia both, to inorganic matter, and consequently to each other ; so that, 

 in the lowest forms of life, all traces of organization disappear, and the three great 

 kingdoms of nature, like three converging radii, meet, and blend ia a common 

 centre. 



12. Vegetation, in some of its forms, appears to be coexten 

 sive with the surface of the earth. It springs up, not only from 

 the sumiy soil, moistened with rain and dew, but even from the 

 naked rock, amidst the arid sands of the desert, in thermal and 

 sulphurous springs, in arctic and alpine snows, and from the beds 

 of seas and oceans. 



a. Among the multitude of natural causes which affect the growth of vegeta- 

 tion, the action of the sun, through the light and heat which it imparts, is the most 

 efficient. This is most powerful at the equator, and gi-adually diminishes in in- 

 tensity, as we proceed from thence towards either pole. Vegetation, therefore, 

 arrives at its highest degree of luxuriance at the equator, and within the tropics. 

 In the temperate zones it is less remarkable for the beauty and variety of its 

 flowers, and the deliciousness of its fruits, than in the torrid ; yet it is believed to 

 be no less adapted to promote the arts of civilized life, and the well-bemg of man 

 in general. In still higher latitudes, plants become few, and of stinted growth, 

 until finally, within the ai'ctic cnclcs, they apparently, but not absolutely, cease 

 to vegetate. 



b. Since climate is affected by elevation above the level of the sea, in the same 

 manner as by increase of latitude, we find a sunilar diminution of vegetable 

 activity, in ascending high mountains. Thus, the peak of Tenei-iffe, situated on 

 a fertile island, mthin the tropics, is clothed, at different elevations, with plants 

 peculiar to every latitude, in succession, from the tonid to the frigid zones, 

 while the summit, being always covered Avith snow, is as barren as the region of 

 the poles. So also the White Mountains, in New Hampshire, exhibit upon their 

 summits a vegetation similar to that of Labrador, or even Greenland. 



c. One of the first requisites for the grovrth of plants, is a soil, from which, by 

 means of roots, they may derive their proper nutrunent and support. But numer- 

 ous species of lichens and mosses find then- most congenial habitations upon the 

 bare rock. The coral island no sooner arises to the surface, than it an-ests the 



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