Vegetable Geography. 239 



jj ne principles, both by their leaves and roots, from which those 

 like Roccella fuciformis exist upon rocks exposed to the sea air, 

 and appear to absorb by their leaves alone ; and finally, a third 

 class such as Eryngiurn Campestre, which do not require salt 

 water, but which live on the seacoast and elsewhere, because 

 their constitution is so robust that they are not affected by the 

 action of salt. 



2d. Marine plants, which live either plunged in salt water or 

 floating on its surface. These are distributed over the bottom 

 of the sea or salt water, in proportion to the degree of saltness, 

 agitation, continuity of immersion, tenacity of soil, and perhaps 

 also the intensity of light 



3d. Aquatic plants, living plunged in fresh water, either en- 

 tirely immerged, as confervac, or lloating on its surface, as stra- 

 tiotes; or fixed in the soil by their roots, with the foliage in the 

 water, as several kinds of Potamogeton ; or rooted in the soil 

 and either floating on its surface, as Nympha?, or rising above 

 it, as Alisma plantago. 



4th. Plants of fresh water marshes, and of very wet places. 



5th. 



u 



" meadows and pastures. 



6th. 



a 



" cultivated soil. 



7th. 



u 



M rocks. 



8th. 



U 



" sands or very barren soil. 



9th. 



U 



" sterile places. 



10th. 



a 



which follow man, azotized matter necessary for 

 their existence. 



11th. 



u 



of forest. 



12th. 



u 



" bushes and hedges. 



13th. 



u 



" subterranean. 



14th. 



u 



" mountain. 



15th. 



<< 



" parasitical. 



16th. 



a 



" falsely. 



These are De Candolle's sixteen stations, but Lindley does 

 not seem to attach much importance to them, because, says he, 

 they are vague and uncertain of application, and frequently 

 common to many plants, but it is nevertheless useful to have in 

 mind that such distinctions do exist, and to point them out when- 

 ever they take any decided peculiarity of character. 



• The next, and by far the most important head under which 

 the geographical distribution of plants is to be considered, is 



