THE ANGIOSPERMAE 



1403 



Fig. 1298. — Casuariua suheroso. A, Part of the nucellus in longitudinal section, 

 showing the mass of sporogenous cells, many of which function as embryo sac 

 mother cells. B, Elongation of the sporogenous cells into the chalaza. One has 

 been transformed into a tracheid. C, Partial development in a non-functional 

 sporogenous cell. D, Egg apparatus at the micropylar end of an elongated 

 sporogenous cell, now an embryo sac. {After Treiib.) 



Fig. 1299. — Qiierciis velutiua. A, Nucellus showing extent and position of the 

 archesporial cells. B, Enlargement of an archesporial cell which develops 

 directly into an 8-nuclear embr>'o sac. (After Conrad.) 



