76 fLAKT LIFE OK THE FARM. 



to the light. The starch in a wheat grain, for instance, 

 is not actually formed within the seed it is formed in 

 the leaves and conveyed from them to the seed. But 

 starch is insoluble ; therefore, before it can be conveyed 

 from the place where it is formed to the place where it is 

 to be stored, it must be rendered soluble, and this change 

 is effected by a process of fermentation resulting in its 

 conversion into soluble " glucose." Arrived at the seed, 

 the glucose is turned back into insoluble starch to be 

 reserved for use when required. The process is essentially 

 the same in the case of the tuber of the potato, the 

 "bulb" of the turnip, or the root of the mangel. All 

 these organs are severally storehouses wherein food is ac- 

 cumulated for future use. The food is neither made nor 

 elaborated in them, but simply stored, having been 

 formed in the leaves and conveyed to the storehouse. 

 At one time, therefore, the leaves and stem may be full 

 of starch, at another, they may be destitute of it, owing 

 to its having been transferred to the seed or the bulb. 



While the origin of the starch is now well known and 

 the processes connected with its formation and transport 

 fairly understood, it is not so with the nitrogenous mat- 

 ters. The nitrogen, as we have seen, enters the plant by 

 the root, and is, therefore, not directly dependent on 

 light or chlorophyll action. Nitrogenous compounds are 

 not formed in the seed, but conveyed to them just as the 

 starch is. 



The carbonaceous reserve-materials that is, the starch, 

 the sugar, the oil, the coloring matters are all the direct 

 result of the action of the green matter acted on by light; 

 the starch and the sugar are essential requisites for the 

 building up of the cell-membrane, the albuminoid or 

 nitrogen-containing substances being, in their turn, es- 

 sential to the formation of the protoplasm, and of the 

 chlorophyll. 



