GYMNOSPERMS. 



'53 



About the first of April the blepliaroplasts have reached nearly one- 

 half the size they finally attain. They are more or less vacuolate, and 

 the kinoplasmic radiations, which have become more abundant, extend 

 in many instances quite to the plasma membrane of the cell. 



After further growth the generative cell divides into the two cells 

 which develop into the two spermatozoids (Fig. 61, B, and Fig. 62). 

 The blepharoplasts take no part in the division of the nucleus. Al- 

 though their kinoplasmic radiations become fewer, they do not enter 

 into the formation of the 

 spindle, as the latter devel- 

 ops apparently entirely 

 within the nucleus, and is 

 almost mature before the 

 nuclear membrane has dis- 

 appeared. In the spindle 

 stage of this division the 

 blepharoplast is seen to 

 have undergone a noticeable 

 change. It has increased in 

 size and its outer membrane 

 has separated from the con- 

 tents, which are somewhat 

 shrunken. The outer mem- 

 brane has separated into 

 fragments or plates, and 

 appears now as a broken 

 line (Fig. 61, B). The 

 kinoplasmic radiations have 

 almost disappeared. The 

 reticulum of the cytoplasm 

 about the blepharoplast is 

 so arranged as to suggest 

 radiations. It will be 

 remembered that precisely the same phenomenon occurs in Cycas. 



During the anaphase of division the finer structure of the outer 

 membrane, which still consists of a number of segments, is seen to be 

 made up of numerous small granules placed side by side to form the 

 membrane. The central contents, which stained very densely at an 

 earlier stage, have disappeared, giving place to a delicate hyaline 

 reticulum (Fig. 61, B). Webber suggests that the densely staining 

 material which resembled nucleoli in its staining qualities was utilized 



FIG. 62. Prothallium of Zai/tia in which the generative 

 cell has divided. 



The blepharoplasts have separated into granules which are 

 beginning to organize the ciliferous band. The first 

 prothallial cell and stalk cell have become gorged with 

 starch. (The magnification of this figure is only one- 

 half that of A, Fig. 61.) (After Webber.) 



