42 BOTANICAL GAZETTE [juLy 
The mature pollen grain contains but one cell, no prothallial cells 
being present. 
The macrospore mother cell first appears in J. communis one year 
after pollination. The first mitosis taking place within it shows clearly 
the stages characteristic of heterotypic division. 
The contents of the pollen grain divide into antheridial cell and 
tube cell soon after pollination. 
In J. communis the antheridial cell remains in the pollen grain 
and does not divide until April of the next spring. 
In J. virginiana the antheridial cell divides in the early summer of 
the same year in which pollination takes place, and fertilization occurs - 
in the latter part of June or first of July. 
The generative cell and the stalk cell migrate immediately into the 
tube. 
The stalk nucleus passes the generative cell and lies near the tube 
nucleus. 
The generative cell does not divide until after the pollen tube has | 
reached the archegonia and just before fertilization. 
Two similar sperm cells are formed, each hemispherical in shape. 
The female prothallium develops, as in the other gymnosperms, 
by free cell formation in a hollow sphere of cytoplasm. After many — 
nuclei are formed, cell walls are laid down between them. These — 
cells grow toward the center, but before they meet, cross-walls are — 
z 
laid down. 
The archegonia develop from superficial cells at the micropylat : 
end of the prothallium. They are arranged in a group, and the entire ; 
complex is surrounded by a single layer of sheath cells. 
During the same day that the generative cell divides, and pre- 
sumably before its division, the central cel] of the archegonium divides. 
A ventral canal nucleus is formed and remains throughout its — 
life free in the cytoplasm of the egg, that is, no true ventral canal cell 4 
is ever cut off. This nucleus remains at the tip of the egg and, as @ 
rule, soon disintegrates. 
After fertilization the first division occurs before the fusion nucleus 4 
has passed to the organic apex of the archegonium. 
In conclusion I wish to €xpress my sincere gratitude to Professor E 
