GNETALES— GNETUM 



415 



In the two African species, Gnetum africanum and G. buchhol- 

 zianiim, the staminate strobilus has no trace of ovulate flowers. 



The staminate flower consists of a stalk with two anthers at the 

 top and a sheathing perianth at the base. The anthers are uni- 



FiG. 388. — Gnelum gnemon: longitudinal sections with flowers in axils of bracts: A, 

 ovule in ovulate strobilus, showing two integuments and perianth; B, staminate stro- 

 bilus, showing sterile ovule with inner integument and perianth; oldest sporangia at the 

 top; C, staminate strobilus with functional sporangia at the bottom; sporangia near the 

 large ovule, in which the gametophyte has reached the free nuclear stage, are abortive; 

 X23. — From Coulter and Chamberlain, Morphology of Gymnos perms'^'* (University 

 of Chicago Press). 



locular. In the development of the microsporangium, the tapetum 

 is formed from the sporogenous tissue and not from the wall cells. 

 There is no endothecium. As the microsporangium matures, all 

 cells between the spores and the epidermis break down, and the 



