26 SEED-FOOD. 



food-supply is deposited within the embryo during 

 the formation of the seed. 



In the various kinds of eggs there is scarcely 

 any difference in the nature of the food-supply. 

 Chemically considered, the contents of a hen's egg 

 is practically the same as that of other eggs. It- 

 is not so, however, with the food-supply of seeds, 

 for very various substances are made use of by 

 different plants. Among these the most important 

 are starch, oils, and albuminoids. 



Starch forms about a third of the bulk of beans 

 and peas ; from half to two-thirds of wheat, oats, 

 rye, and barley ; and over four-fifths of maize and 

 rice. It is very much like sugar in its chemical 

 composition, and has about the same value as a 

 food. 



Oil occurs in small quantities along with the 

 starch in the seeds just mentioned, but in many 

 cases it entirely replaces the starch, and forms the 

 principal part of the seed-food. Peanuts and cot- 

 ton seeds, for example, are very rich in an oil 

 which is extensively used as a substitute for that 

 obtained from olives. Walnut oil is put to the 

 same use. Flaxseeds afford the linseed oil so val- 

 uable as a medium for mixing paints. The albu- 

 men of the coco-nut when boiled and pressed yields 



