586 



MORPHOLOGY OF GYMNOSPERMS 



longest one known among gymnosperms, and it is associated with the 

 deepest pollen chamber. It follows that although the pollen grains 



Figs. 433-435. — Ephedra trifurca: development of the archegonium; fig. 433, 

 the neck («) and central cell; X500; fig. 434, three tiers of cells in the neck, the central 

 cell not yet divided; Xsoo; fig. 435, later stage, in which the neck can scarcely be 

 distinguished from the surrounding cells; the central cell (r) still undivided; X112. — 

 .\fter L.\KD (18). 



rest upon the neck of the archegonium, there remains much tissue for 

 the tubes to penetrate. 



