DEVELOPMENT. 77 



Germination* The conditions under which germina- 

 tion takes place need not be alluded to at any length, as 

 they are the same as those requisite for growth, and 

 practically every cultivator knows that air (oxygen), 

 moisture, and heat, varying in amount according to the 

 plant and according to circumstances, are required, and 

 that his success depends in great measure upon the 

 proper tillage of the soil which secures these requisites. 

 When the seed, or rather the embryo plant within it, 

 begins to grow, water is absorbed, the seed swells, the 

 insoluble starch stored up becomes converted into glu- 

 cose, or a form of sugar, by the agency of a nitrogenous 

 substance which acts as a ferment. These chemical pro- 

 cesses are accompanied by an evolution of heat and an 

 outpouring of carbonic acid gas. Thus is it that in malt- 

 ing 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 



