34 BOTANICAL GAZETTE [JULY 
germination of the pollen grain before it reaches the nucellus, or it may 
be that the pollen tube finds difficulty in piercing the tissue of the 
nucellar cap, and in the effort to do so the pollen grain end is pushed 
up into the pollen chamber. From the appearance of the pollen tube 
lying in a horizontal plane on the nucellar cap before the tip enters 
the nucellus, it seems quite probable that the latter explanation is the 
more suitable one. 
The following spring the antheridial cell divides to form two nearly 
similar cells, the stalk and the generative cells. The division was 
not observed, but on May 8 the two cells had been formed and were 
seen in the pollen grain portion of the male gametophyte (figs. 9, 10). 
NorEN gives no figure illustrating this stage and speaks only of a 
stalk nucleus. The two cells soon move down the tube. At first 
they are very similar in appearance, but in a short time the generative 
cell is easily distinguished by its larger nucleus, and by the fact that 
it retains its own cytoplasm; while that of the stalk cell is not dis- 
tinguishable after passing into the tube, as in Thuja (LAND 14) 
(figs. 9-12). Not until after the stalk nucleus has passed the genera- 
tive cell does the nucleus of the latter appear larger than either the 
stalk or the tube nucleus (fig. 12). At this time the generative cell 
increases rapidly in size, and its nucleus becomes several times larger 
than either of the other two nuclei. The.difference in size of these 
nuclei is more marked in J. communis (fig. 13) than in J. virginiana 
(figs. 11, 12). Neither in J. communis nor in J. virginiana is it pos- 
sible, as stated above, to detect the cytoplasm of the stalk cell in the 
pollen tube. That the entire cell loses its connection with the wall of 
the pollen grain and starts into the tube is clearly shown in fig. 10. 
But very early in its downward course its cytoplasm fuses with the 
general cytoplasm of the tube and can no longer be distinguished 
from it. 
The end of the tube with its cytoplasmic contents advances toward 
the female prothallium and spreads over the upper end of the arche- 
gonial complex (fig. 27). The generative cell takes its position in 
the center of the tube near the tip, and strands of protoplasm extend 
from it to the lateral walls of the pollen tube and below to the tip. 
The stalk and the tube nuclei, which are usually of the same size and 
can no longer be distinguished from each other, are side by side below 
