148 



ARCHEGONIATES. 



plane of division of the generative cell. In Fig. 58, E, which repre- 

 sents a median section through the two daughter-cells, the blepharo- 

 plast has made one turn around the cell. The cilia, which at first lay 

 wholly within the cytoplasm, project out through the plasma membrane 

 as the band approaches the surface of the cell. The nuclear beak, 

 which remains in close contact with the band during its earlier develop- 

 ment, finally becomes separated from it (Fig. 59, C). In the mature 

 spermatozoid the blepharoplast, as already stated, makes about five 

 turns around the cell counter clock-wise. As is evident from a median 



FIG. 59. Further development of spermatozoid in Cycas revoluta. (After Ikeno.) 



A, part of spermatozoid mother-cell showing nuclear beak in contact with granular blepharoplast band. 



B, spermatozoid mother-cell ; band-shaped blepharoplast longer, one end being applied to nuclear beak. 



C, later stage ; blepharoplast has made about three turns about the cell ; the nuclear beak seems to 



have separated from ciliated band. 



D, nearly ripe spermatozoid in median section. Both nucleus and cytoplasm are lobed on one side as 



if constricted by blepharoplast, which describes about five turns around the hemispherical cell. 



section, the mature spermatozoid consists of a large nucleus completely 

 surrounded by a thin layer of cytoplasm, and the blepharoplast lies in 

 a depression or groove (Fig. 59, D). As a result both cytoplasm and 

 nucleus are lobed, thus presenting a wavy contour in section. This 

 phenomenon seems to indicate that during the final increase in size of 

 the nucleus, the blepharoplast acted as a kind of constriction upon the 

 anterior end of the cell. The same is true in both Zamia and Ginkgo. 

 In the mature spermatozoid the cytoplasm which completely surrounds 

 the nucleus is clearly distinguishable. As will be seen for Zamia and 



