326 



GAMETOPHYTE OF CYCADS 



the cell (t) called the tube cell, represents a new departure in 

 the evolution of the male gametophyte. The tube cell grows 

 out into the tissues of the megasporangium forming a tubular 

 structure and often branching extensively and absorbs food for 

 the nourishment of the antheridial cell (Fig. 247, B). This 

 latter cell finally divides, forming a rudimentary antheridium 



E 



FIG. 247. Male gametophyte of Zamia: A, stage of germination of the 

 microspore attained in the sporangium. See text for explanation of figures. 

 B, formation of tube for absorbing of food from megasporangium. C, 

 spore end of gametophyte showing the antheridial cell dividing into a body 

 cell, b, and a single-wall cell, w. D, the body cell has divided, forming 

 two cells, which become the male gametes. E, spore end of male gameto- 

 phyte, showing the spirally ciliated male gametes. After Webber. 



consisting of but a single wall cell (w) and a body cell (6), 

 which by division forms directly two huge male gametes with 

 spirally arranged cilia (Fig. 247, CE). Owing to the growth 



