38 SPERMATOGENESIS AND FECUNDATION OF ZAMIA. 
Both the first prothallial cell and the stalk cell have become filled 
with numerous starch grains, which are frequently compound (fig. 21), 
and a cross section of the tube through these cells at this stage (fig. 23) 
presents a puzzling structure until the method of development of the 
interior first prothallial cell is understood. Even in this greatly 
enlarged mature stage the original end of the attachment of the first 
prothallial cell with the old pollen grain remains the same size as in 
the early stages (compare figs. 20 and 21), and the point of attachment 
of the plasma membrane of the second prothallial cell (now a part of 
the plasma membrane of the stalk cell) is the same distance from the 
point of attachment to the pollen tube as in the early stages (fig. 21). 
The central cell, which just after its formation by the division of 
the second prothallial cell was about 16.91 4 long by 15.57 mu wide, 
and which at the time the blepharoplasts appeared had reached a 
diameter of about 36 “, now commonly measures 170 / in width by 
190 / in length. Its size, however, is very variable. The blepharo- 
plasts in which greatest interest centers have also increased greatly 
in size, in this stage measuring from 18 to 20 / in diameter. In many 
instances, probably in the majority of cases at this stage, they have 
become somewhat compressed at the poles, so that they are more or 
less elliptical in equatorial section (fig. 59) and round in polar view 
(fig. 60). They still retain their positions at the poles of the nucleus, 
lying free in the cytoplasm, in this stage usually rather nearer the sur- 
face of the cell than the nucleus, not infrequently being almost in con- 
tact with the plasma membrane, which is frequently somewhat indented 
immediately above them. In the course of the development the con- 
tents of the blepharoplasts, which was at first homogeneous and then 
slightly vacuolate, has become filled with vacuoles which present a 
beautiful, regular form. A few highly refractive bodies, presenting 
the appearance of crystals or crystalloids of some sort, are also fre- 
quently observed in the blepharoplasts at this stage (fig. 29), but the 
writer has been unable to learn anything as to their nature or function. 
In this stage the kinoplasmic radiations have become very numerous 
and extensive, and are more slender than in earlier stages. They radi- 
ate in all directions from the blepharoplast, but are naturally more 
strongly developed and longer on the sides than above toward the sur- 
face of the cell or below toward the surface of the nucleus The writer 
has tried to determine how the increase in number of radiations is 
brought ‘about, but has been unable to solve the problem. He has 
found no evidence, however, favoring their increase by division, as 
claimed by some investigators. The cytoplasm of the central cell in 
this stage has become much more dense than in the preceding stage 
described, but still presents a beautiful reticular structure in well- 
stained sections. The distinction between kinoplasm and trophoplasm 
here is not well marked; indeed, in no place in the development of 
