The Plantlet. 41 
59. No Food can be formed Without Chlorophyll. 
By the agency of chlorophyll, the chlorophyll bodies absorb 
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 recom- 
bine them into foods of various kinds which can be used by 
the protoplasm in making new parts and in repairing waste. 
This process is known as Assimilation (as-sim’-i-la’-tion). 
Until assimilation commences, no new plant substance has 
been formed. It is true that new cell-walls and new pro- 
toplasm may be formed from the food supply of the seed 
before chlorophyll appears, but until chlorophyll is formed, 
and assimilation begins, the whole plantlet, with whatever 
remains of the seed, when dried, weighs no more than the 
seed weighed at the beginning. The material formed by 
assimilation is starch, or some substance of similar compo- 
sition (sugar or oil), which, after undergoing chemical 
changes, if need be to render it soluble, is distributed to 
other parts of the plant to be built up into cell-walls and 
protoplasm, or to be held as reserve food (14). 
Only plants can assimilate food from pr 
mineral substances. The food of ani- f Bae 
mals must all have been first assimilated } 
by plants. pit J 
60. The Sources of Plant Food. 
By observing plantlets of the bean or 
pumpkin a few days after germination, 
we may discover that the cotyledons, fFic.14. showing starch 
which were at first so plump, have shriy- ¢'Yst#ls stored as reserve 
food in cell of potato. 
eled to a mere fraction of their former Highly magnified. 
size. This change is due to the fact that the food con- 
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