64 Dr Seller on the Nutrition of Plants. 



prevalent kinds of saline matter in the vegetable kingdom, 

 exist in small proportion, diffused through the rocks of the 

 crust of the earth. ' These can get into the soil only by the 

 slow crumbling down of the rocky fragments which contain 

 them. A quick succession of crops, requiring a large propor- 

 tion of such saline constituents, will so far exhaust a soil of 

 the parts already sufficiently comminuted to afford them ; 

 and thus the next crop will be inferior to the former. In 

 process of time, the comminution proceeds ; and then the pre- 

 vious fertility, in as far as it is dependent on this cause, re- 

 turns, or it is restored at once by the same saline constitu- 

 ents being contained in the manure applied. 



One thing, at least, is already certain, that the phosphates, 

 which exist so abundantly in the animal kingdom, have no 

 other source but the rocks of the crust of the earth. By the 

 crumbling of these rocks they pass into the soil, from the 

 soil into plants, and from plants, in the composition of vege- 

 table food, into animals, from the excretions of which they 

 pass again into the soil. The general admission of this last 

 proposition is of very recent date, and has cost a great 

 struggle. The contrary was taught by Schrader and Bran- 

 connot at the beginning of this century, and their views seem 

 to have taken possession of the minds of naturalists, not- 

 withstanding the opposition of the more philosophic De 

 Saussure. 



It is forty years since De Saussure exclaimed, " analysis 

 demonstrates, that all the prevailing substances in the ashes 

 of plants are contained in the soil ; and that its soluble part, 

 which alone penetrates into the vegetable economy, contains 

 these substances in greater proportion than the insoluble 

 part." Again, he says, " the explanations which I can give 

 on this point are sometimes far from being pei-fectly satis- 

 factory. These often require a knowledge which I have not 

 attained — that of the vegetable organism. But they are less 

 absurd than those which ascribe to plants a creative power 

 as respects their elements."* 



* Recherches Chimiques sur la Vegetation par Theod. De Saussure. 

 A Paris, 1804, p. 284. 



