34-0 



SEED OF PIXE 



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

 bryo, pronounced changes occur in the sporangium. It steadily 



I 3b 



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

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

 suspensory 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. 3A, section of 

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

 2,B, 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- 



Fig. 257. Sectional view of pine seed: /. hard integument; g, gameto- 

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

 sporangia! tissues. The embryo consists of a root, r, ensheathed in a 

 large root cap. cotyledons, r, and stem, s. 



