290 BOTANICAL GAZETTE [APRIL 
so-called double gametophyte (figs. R-U and 28, 29, 31, 32); when 
the first primary derivative is surrounded by cytoplasm it divides, 
giving rise to a spermatogenous and a sterile cell (figs. K-M and 
9, 12, 30). In this case there is no further division of the primary 
cell; the first primary derivative becomes the functioning antherid- 
ial cell. Again, if the first cell cut off contains sufficient protoplasm 
it may divide once or even twice to form as many as four free 
nuclei. When this occurs, the primary cell soon ceases to divide 
and begins to disintegrate (figs. N-Q and 28, 29, 33). The first 
primary derivative may function as an antheridial cell by directly 
dividing to form a spermatogenous and a sterile cell, by repeatedly 
dividing to form a number of free nuclei, or by becoming primary 
in nature and hence developing along with its sister cell to form a 
bi-antheridial gametophyte. 
When the first primary cell is evanescent, a second primary 
division takes place. Nor is it uniform. Frequently the primary 
cell approaches the first primary wall before dividing, and it may 
come into contact with this wall. The second primary derivative 
is then cut off as a lenticular cell against the wall of the first and 
soon disintegrates (figs. C-E and 23, 25, 26). If, however, it remains 
imbedded in the cytoplasm of the primary cell, it divides to form 
a spermatogenous and a sterile cell (figs. F-I and 25, 38). Hence 
the second primary derivative may function as an antheridial cell. 
When, as it has been hitherto described, the first and second 
primary derivatives are evanescent, a third primary division takes 
place, and the last cell cut off functions as the antheridial cell 
(figs. A-E and 42-51). 
Since the spermatogenous cell may originate from the first, 
second, or third primary derivatives, we are forced to the conclusion 
that these cells are all potentially antheridial, one or in some cases 
two functioning as such. They may be known as evanescent or 
functioning antheridial cells, as the case may be. 
Development; time; nutrition 
Growth is exceedingly rapid; in three days the diameter of the 
pollen grain is doubled, its volume becoming four times as great. 
In Pinus “the mature pollen grain has the same size and form a5 
