DEVELOPMENT OF PLANTS 



357 



root cap (Fig. 256, 3). Attending this formation of the em- 

 bryo, pronounced changes occur in the sporangium. It steadily 



Fig. 256. Development of the young sporophyte or embryo: 2, diagram 

 of a section of a megasporangium, showing the formation of elongated sus- 

 pensory cells and numerous embryos, e; i, integument; sp, sporangium nearly 

 consumed by the growth of the gametophyte; g, gametophyte, the central 

 portion of it disorganized by growth of embryos, e. 2,A, section of a 

 nearly mature embryo; s, suspensor; r, root cap; c, cotyledons; st, stem. 35, 

 external view of embryo. 



increases in size and the integuments become modified into a 

 hard coat, or the outer layer may be pulpy, as in some of the 

 cycads. The gametophyte also increases in size, and as the em- 



Fic. 257. Sectional view of pine seed: i, hard integument; g, gameto- 

 phyte, often called the endosperm, which has completely consumed the spor- 

 angial tissues. The embryo consists of a root, r, ensheathed in a large root cap, 

 cotyledons, c, and stem, s. 



