The Plantlet. 43 



sorb energy in the form of light. Tliis 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-lation) ) . Until this food preparation commences, no 

 7iew 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 chloro- 

 phyll is formed, and food prepara- 

 tion begins, the whole plantlet with^ 

 whatever 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 fir. le. showint; 



starch crystals stored 

 some substance of similar COmpOsi- *>« reserve food in a 



^ cell of potato. Highly 



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

 dergoing chemical changes if need be, to render it 

 soluble, is distributed 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 



