DEVELOPMENT. 79 



absorbed, the seed swells, the insoluble starch stored up 

 becomes converted into glucose, or a form of sugar, by the 

 agency of a nitrogenous substance which acts as a ferment. 

 These chemical processes are accompanied by an evolution 

 of heat and an outpouring of carbonic acid gas. Thus is it 

 that in malting barley the grain swells, gets hot, and its 

 starch is converted into sugar. As the seedling grows, 

 both starch and sugar gradually disappear, although the 

 stock of starch is continually replenished so long as the 

 leaves continue to act. The nitrogenous constituents of 

 the seed undergo similar changes from the insoluble to the 

 soluble condition, the latter being capable of transport from 

 place to place as may be required. 



The accumulation of insoluble matter in the seeds is 

 accounted for by M. Deherain in this wise. At the period 

 of maturation the juices of the plant contain the various 

 substances held in solution. These juices are directed 

 towards the seed or towards the store-organs, wherein, by 

 virtue of some changes not fully understood, the matters 

 previously held in solution become as it were precipitated 

 and rendered for the time insoluble. As a consequence, 

 the water is deprived of these materials, and to restore the 

 balance fresh supplies are drafted from the leaves towards 

 the store-organs, there in like manner to deposit their 

 starch, their inulin, or albuminoid matter. In the case of 

 biennials like turnips, or mangels, during the first season of 

 growth, the leaves collect and form the nutritive matters 

 which are subsequently transferred to the " root," and the 

 store so accumulated is utilised the following season in the 

 formation of flowers and seeds, as before explained. 



Growth, then, in a chemical sense, may be said to consist 



