GYMNOSPERMS. 151 



cell (body cell) (Fig. 60, E). In this figure the division is in the 

 telophase, the two daughter-nuclei being still connected by the con- 

 necting fibres. Owing to the crescent shape of the cell the spindle 

 lies at an angle to the major axis of the prothallium, the lower nucleus 

 being crowded to one side by the position of the first prothallial cell, 

 while the upper nucleus occupies a central position in the upper half 

 of the cell, which, when the wall is formed, will become the genera- 

 tive cell (body cell, central cell). The lower nucleus becomes the 

 nucleus of the stalk cell. Fig. 60, F, represents the next stage in 

 which the division is complete. A distinct transverse plasma mem- 

 brane is formed just above the apex of the first prothallial cell which 

 is almost entirely surrounded by the stalk cell. It is clear that should 

 the plasma membrane separating the generative from the stalk cell be 

 very delicate and somewhat obscured, the nucleus of the stalk cell 

 would appear to be forced out to one side. For this reason it seems 

 possible that the plasma membrane separating stalk and generative 

 cells in Cycas was overlooked by Ikeno. In Ginkgo the first prothal- 

 lial cell, which according to Webber is also surrounded by the stalk 

 cell, was considered by Hirase ('98) to be strands of cytoplasm in the 

 second prothallial cell. Miyake ('02), who has also examined Ginkgo, 

 confirms the observations of Webber. 



At the stage of Fig. 60, F, according to Webber, the nucleus of the 

 generative cell is 9.79 //. in diameter, that of the stalk cell 7-12 /z, while 

 the first prothallial cell is 8.97,1 in diameter. The entire prothallium 

 is 29.37 f 1 l n g by ^6.91 fj. wide. 



Neither during the division of the second prothallial cell into stalk 

 and generative cell nor for some time afterward was anything observed 

 in the cell in connection with the spindle, or elsewhei-e, that suggested 

 a young blepharoplast. It is not until the generative cell has increased 

 considerably in size that the first traces of the blepharoplasts were recog- 

 nized. At first each blepharoplast consists of a small, deeply staining 

 granule, from which several filaments of kinoplasm radiate, following 

 the meshes of the cytoplasmic reticulum (Fig. 60, G). " The central 

 granule (Webber, '01, p. 31) does not seem to be different in sub- 

 stance from the radiations stains the same and shows no differentiation 

 of structure. In this stage it is only a half micron in diameter or less, 

 and seems to be scarcely more than the point of the crossing of the 

 filaments of kinoplasm. These granules are located in the cytoplasm 

 about halfway between the nucleus and the cell- wall. Two are 

 formed in each central cell at the same time and apparently inde- 

 pendently. They are commonly located on the opposite sides of 



