DIFFERENCE IN DEVELOPEMENT. 59 



matter was altered. In the plant growing in water, 

 there was a constant decrease of uriazotised matter ; 

 while in the other a certain quantity of that substance 

 was generated anew. Nothing can be more certain 

 than that in Boussingault's experiments, the first-formed 

 leaves acquired by the supply of mineral substances the 

 faculty of absorbing and decomposing carbonic acid, a 

 power not possessed by the plant developed in pure 

 water ; and that as much soluble unazotised substance 

 was reproduced as had been consumed in the formation 

 of the leaves and roots by the conversion into cellulose 

 of the store originally present. 



In the movable constituents of the plant, the rela- 

 tive proportion between the unazotised and the azotised 

 seed constituents was manifestly restored pretty nearly 

 as it existed in the seed ; both matters passed through 

 the stem into every new-formed leaf-bud, and took part 

 in the developement of new leaves, by whose operation 

 the consumption of unazotised matter was always made 

 good again within a certain limit, so that the same pro- 

 cess could be repeated again and again for months. In 

 every one of the dead leaves (and root fibres) a certain 

 quantity of the azotised substance remained behind, and 

 in the last period of vegetation the floating remainder 

 of this substance was collected in the pod and in the 

 seeds. 



The supply of mineral substances had served to 

 effect the continuance of the chemical process, and 

 caused the production of unazotised substances. By 

 the presence of these mineral bodies, and by the coop- 

 eration of the azotised matters, new material was en- 

 gendered from carbonic acid to form the cell-walls, and 

 the term of life was prolonged to its proper limit. The 

 most remarkable point is, that a quantity comparatively 

 so small, of azotised substance derived from the seed, 

 should so long be able to perform its assigned functions, 

 apparently without suffering any alteration ; so that in 

 the body of the living plant, made to produce and col- 

 lect it, it would seem to possess a kind of indestructi- 

 bilitv. 



