142 Plant Biology 



usually present. The male cones are composed of microsporophylls, while 

 the female cones are composed of megasporophylls. The ovules (im- 

 mature, unde\eloped seeds), and later the true seeds, are borne exposed 

 on the female megasporophylls. 



Fig. 54. — Cycads. Cycas (above) with a crown of young leaves unfolding; 

 male plant of Zamia (lower left) at the time of "flowering"; mature fruiting plant 

 of Zamia (lower right). (From Weatherwax: Plant Biology, W. B. Saunders 

 Co.) 



Two types of spores (heterospory) are formed; namely, microspores, 

 which develop into male microgametophytes, and megaspores, which 

 develop into female megagametophytes. 



Pollination occurs by wind, the pollen being carried near the micropyle 

 (mi'kropile) (Gr. mikros, small; pyle, gate) or little opening of the 



