GYMNOSPERMIA 



307 



dioecious, achlamydeous, and at the summit of the 

 stem. In Zamia the male and female flowers form 



Figr. v^.—Cycas revohda (after Strasburger) 



long cone-like spikes, 

 are crowded peltate 

 stalked, bearing pollen-sacs (micro- 

 sporangia) in clusters on their under 

 surface. In Cycas the female flowers 

 occupy the apex of the stem, and form 

 a much less distinctly cone-like struc- 

 ture than in Zamia. The carpels in 

 Cycas (fig. 277) are small, pinnate or 

 pinnifid leaves, the lower pinnae or 

 leaflets of which are replaced by 

 ovules (macrosporangia). 



The Cycas are a very old group of 

 plants, especially characteristic of 



In male flowers the stamens 

 scales, often 



Figp. 377.— Carpellary 

 Leaf of Cycas reroUtta 

 (after Strasburger) 



o. Ovule. 



the IMesozoic 



Periods, having attained their maximum development 



