1 86 GROWTH AND WORK OF PLANTS 



walls make the seed; but in the grain of wheat, corn, etc., the wall 

 of the ovary is fused with the walls of the ovule, making the ripe 

 grain. In the water lily, the pepper, and some other plants, a part 

 of the interior of the ovule is left in the seed. This is called peri- 

 sperm when it is present in the seed, so that in such a seed there 

 are embryo, endosperm, and perisperm surrounded by the integu- 

 ments or ovule walls. 



306. Albuminous and exalbuminous seeds. In the study 

 of the substances stored in the grain of corn and wheat it was 

 found that there is a large quantity of starch in the endosperm. 

 This is an albuminous substance. Seeds containing endosperm 

 at ripeness are called albuminous seeds, while those like the bean, 

 pea, etc., with no endosperm are called exalbuminous. 



