9- 9 



Class I. CYCADALES. 



Fam. i. CYCADACEAE. 



Subt'.mi. ZAMIEAE. 

 (Plates 14, 15, 16.) 



Plants with simple or slightly branched, woody stems 

 and terminal tufts of pinnate leaves. Dioecious. 



Male flowers cone-shaped, solitary or in a whorl of 

 3-5 at the apex of the stem. Each cone composed of a 

 large number of spirally arranged scales (sporophylls), which 

 bear numerous pollen bags on their under side. When the 

 cone is ready for pollination the axis elongates a little, thus 

 separating the scales to some extent and exposing the pollen 

 bags, which open by a longitudinal slit. The pollen grains 

 cohere in lumps to some extent. 



Female flowers cone-shaped, solitary or in a whorl at 

 the apex of the stem, about twice as thick as the ? cones, 

 each one consisting of a large number of spirally arranged 

 ovuliferous scales. Each scale consists of a winged stalk 

 with an enlarged, more or less peltate apex, from which, on 

 the upper side of the stalk, two ovules are suspended, the 

 micropyle being turned towards the axis of the cone. The 

 ovule is fully developed only when it has reached almost 

 the size of the ripe seed; it then secretes a drop of fluid 

 at the micropyle, by means of which the pollen grains, 

 brought there either by the wind or through the agency 

 of insects, are captured and transported into the pollen 

 chamber; here they attach themselves to the walls of the 

 chamber by means of a short tube {haustorium) . Their 

 further development has not been observed in any South 

 African species as yet, but in Cycas each pollen grain 

 develops two spermatozoids, which are provided with 

 several tufts of cilia, by means of which they are able to 

 move about in the fluid of the pollen chamber. The 

 spermatozoid attaches itself to the apex of the nucellus, 

 when its contents, by entering the latter, finally reach the 

 oosphere. (Fig. 62, Nos. 4 and 5.) 





