SEED-BEARING PLANTS 
397 
sporophyll, Fig. 295). In the Cycads and higher plants 
the megasporangia are called ovules. 
365. Ovules. The young megasporangia or ovules of 
Cycads consist of two distinct regions of sterile tissue an 
inner nucellus, and an outer covering, or integument, 
FIG. 293. Megasporophyll (carpel) of Cycas media, bearing one ripe 
naked (gymnospermous) seed, and three ovules which failed to become 
seeds, doubtless through not being fertilized. (Compare Fig. 292.) 
which is an outgrowth of the ovule just below the nucellus. 
The integument serves to protect the more delicate tissues 
within, and later becomes transformed into the seed- 
coat (Figs. 296298). Only one of the four megaspores 
develops within the nucellus. 
366. Female Gametophyte. As in Selaginella, the mega- 
spores begin to germinate while still in the sporangium, 
but now a new feature is introduced into life history; 
