THE PLANT AS A WORKING MACHINE 



17 



plant absorbs food material from the ovule. While the em- 

 bryo plant is developing, food material is constantly being 

 transported into the grain, or ovule, until finally a relatively 

 large amount of food material is thus deposited (fig. 12). 

 The ripened seed, or grain, consists of the old ovule wall, 

 the stored food material, and the embryo corn plant. The 

 scale-like bract, or chaff, which surrounded the young ovule, 

 often adheres to the ripened grain. In many kinds of plants 



starch 7L75% 



water 10.75% 



proteins 10% 

 "oil 4.75% 



A 



FIG. 12. Grains of Indian corn 



A, a grain with seed-covering partly torn away, showing the root tip (r) and the 



stem tip (s) of the emhryo corn plant within the seed. B, a grain showing the 



percentage of different substances that compose it 



the ripened seed or seeds may be surrounded by one or more 

 structures, the whole then composing the so-called fruit. 



14. Seed germination. Seeds may lie dormant for a very 

 long time or may grow soon after being formed. Under 

 favorable conditions the young plant within the seed bursts 

 the seed coat and continues its growth as a new plant. It 

 pushes out its root, stem, and leaves and soon assumes the 

 appearance of the kind of plant that formed it (figs. 13 and 

 14). In^some kinds of plants, when the seed germinates, the., 

 seed coat remains underground and the stemand leaves grow 



