396 



STRUCTURE AND LIFE HISTORIES 



nately divided blade, with mid-rib and petiole (Fig. 292). 

 The genera that bear the megasporophylls on the main 

 stem resemble the ferns, and in this respect are the simplest, 

 or most primitively organized, of all living seed-plants. 



364. Megasporangia. Unlike the microsporangia, the 

 megasporangia of Cycas occur, not in groups, but solitary 



FIG. 292. Young megasporophyll (carpel) of Cycas revoluta, bearing 

 six young ovules, destined, after fertilization, to mature into seeds. Note 

 the relatively large amount of leaf-blade above the ovules, as compared 

 with Cycas media (Fig. 293). (Specimen from C. C. Chamberlain.) 



on the lower part of the sporophyll, at the margin, occupy- 

 ing the position of the pinnate divisions (Figs. 292-294). 

 In genera bearing carpellate cones the megasporangia 

 occur in pairs on the under surface of each scale (mega- 



