The Plantlet. 43 



sorb energy in the form of light. This energy the 

 chlorophyll body uses to take to pieces the carbonic 

 acid, mineral salts and water absorbed from the air and 

 the soil, and to recombine them into foods of various 

 kinds which can be used by the protoplasm in making 

 new parts and repairing waste (Assimilation (as-sim'- 

 i-la-tion)). Until this food preparation commences, no 

 new plant substance has been formed. It is true that 

 new cell-walls and new protoplasm may be formed from 

 the food supply of the seed before chlorophyll appears, 

 but until chlorophyll is formed, and food preparation 

 begins, the whole plantlet with what- 

 ever remains of the seed, when dried, 

 weighs no more than the seed 

 weighed at the beginning. The ma- 

 terial formed for food is starch, or 

 some substance of similar composi- 

 tion (sugar or oil), which, after un- 

 dergomg chemical changes if need 

 be, to render it soluble, is distrib- 

 tributed throughout the plant to be 

 built up into cell-walls and protoplasm, or to be held 

 as reserve food (14). 



Food preparation and assimilation are not necessarily 

 simultaneous, but either may proceed without the other. 

 Only plants can prepare food from mineral sub- 

 stances. The food of animals must all have been first 

 formed by plants. 



59. The Sources of Plant Food. By observing plant- 

 lets of the bean or pumpkin a few" days after germina- 

 tion, we may discover that the cotyledons, which were 



