DEVELOPMENT. V7 



The seed, then, in addition to the young plant, con- 

 tains in the tissues of the embryo plant itself, or in the 

 perisperm surrounding it, reserve-materials destined to 

 supply the young plant with food during its growth and 

 development. 



Reserve-materials: their Transport Under the head 

 of nutrition, mention has been made of the substances 

 formed in plants through various agencies. Some of these 

 are used up at once during growth, while others are 

 reserved for future use, having usually undergone some 

 change in constitution to fit them for their purpose. 

 Speaking broadly, these reserves are either starchy, oily, 

 or albuminoid (nitrogenous) in their character. The 

 starchy or oily ingredients are the direct products of the 

 action carried on under the influence of sun light in the 

 cells containing chlorophyll. Starch cannot be formed in 

 cells containing no chlorophyll, nor, for a continuance, in 

 chlorophyll-containing cells, unless they are exposed 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 con- 

 veyed 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 



