1909] ' OTTLEY—JUNIPERUS 33 
more than two weeks in the time at which the pollen may be shed. 
The microspore in J. communis and in J. virginiana undergoes no 
division in the anther, and so far as I have been able to determine 
no prothallial cells are ever formed in them. This agrees with the 
condition found in J. communis (BELAJEFF 2, NOREN 20), in Biota 
and Cupressus (STRASBURGER 27), and in Taxus baccata, J. sphaerica, 
and J. chinensis (CoKER 6). In Thuja (LAND 14), Libocedrus and 
Chamaecyparis (LAWSON 17), a division takes place while the pollen 
grains are still in the anther and gives rise to the tube and antheridial 
cells, but in these also no prothallial cells are ever formed. 
The mature pollen grain has two walls, a deeply staining outer 
one and a faintly staining inner one (fig. 3). The outer wall of the 
pollen grains appears slightly roughened in many instances. When 
pollination takes place, the one-celled pollen grain comes to rest on 
the nucellar cap, the cells of which immediately lose their nuclei and 
become more or less disintegrated and collapsed, forming a depression 
in the top of the nucellus (fig. 6; Nor&n, fl. 1, fig. 5). Fifteen days 
after pollination the microspore divided to form the tube and the 
antheridial cells. The antheridial cell is the smaller of the two and 
remains always at one end of the pollen grain, while the tube cell is 
larger, possesses less dense cytoplasm, and its nucleus occupies the 
center of the pollen grain. Many starch grains are present at this 
time in the tube cell. The nucleus is large, with a loose chromatic 
network, and contains one nucleolus (fig. 5). As described by NoREN 
(20), immediately after the division to form the antheridial and the 
tube cells, the pollen grain germinates, and the tube pushes its way 
down into the tissue of the nucellus, but by June 26 it has reached 
only a short distance. The tube nucleus migrates into the tube, 
but does not reach the end of it until the following spring; whereas 
in J. virginiana the tube nucleus passes at once into the tip of the tube 
(fig. 8), and fertilization takes place in the early summer of the same 
year. 
Soon after germination in J. communis, the exine is shed in the 
pollen chamber and remains there, a dark-blue shell, as has been 
described for Taxodium by CoKER (5). In many cases the pollen 
grain end of the tube is raised up above the nucellar tip.into the pollen 
chamber, giving a peculiar appearance. This may be caused by the 
