Pseudotsuga Dotiglasii . 165 
grains find a lodgement on the apex of the nucellus, and upon germination 
directly penetrate the nucellar tissue. This is certainly not the case with 
Pseudotsuga . Of the numerous preparations examined I was unable to 
find a single case of a pollen grain that had reached the nucellus. They 
were invariably — and sometimes in great number — found in the upper 
chamber of the micropyle and frequently entangled in the hair-like processes 
at the mouth. They are evidently caught on the stigmatic surface when 
the mouth is extended, and when the extremity turns or folds inwards 
as shown in Fig. 3 the pollen grains find themselves enclosed in the upper 
chamber. It will be seen in Figs. 3 and 4 that the stigmatic processes are 
now all pointing backwards towards the interior of the micropyle. It is in 
this upper chamber of the micropyle that the pollen grains commence their 
germination. In Figs. 3, 4, and 10 some characteristic positions of 
germinating grains are shown. 
It will also be observed from these figures that after pollination — 
as a result of continued growth — the whole micropylar region of the 
integument bends or curves towards the ovuliferous scale. This is evidently 
due to the fact that growth of the integument on the side nearest the 
ovuliferous scale is less rapid than that on the opposite side. This irregular 
growth continues until — as indicated in Figs. 4 and 10 — the more distal 
part of the micropyle lies at right angles to the long axis of the ovule. 
The pollen grains remain in the upper chamber of the micropyle 
for a week or ten days before germination begins. This is marked first by 
a rupture of the exine and a slight protrusion of the pollen-tube. It was 
observed that the rupture of the exine and the protrusion of the pollen-tube 
always take place at the side of the pollen-grain directly opposite to that 
occupied by the two degenerated prothallial cells — that is, on the side 
nearest the tube nucleus. In Fig. 3 one may see the position and germin- 
ated condition of the pollen grains as they appeared on April 28. 
The division of the generative nucleus evidently takes place about the 
time the exine is ruptured, and just before the appearance of the pollen- 
tube ; for although the actual dividing stages were not found, the immediate 
results of this division were frequently observed. As indicated in Fig. 2 the 
division of the generative nucleus results in the organization of two distinct 
cells, one of which is considerably larger than the other. The cytoplasm 
of these two cells is much more dense and granular than the cytoplasm 
of the pollen-tube, and each is completely surrounded by a thin but sharply 
defined cell-membrane. The smaller of the two is the so-called stalk-cell, 
while the larger one is the body-cell. The tube nucleus descends with the 
tip of the growing tube, but the stalk- and body-cells remain in their original 
positions for some considerable time. This may be seen in Fig. 2. 
After the conditions shown in Fig 2 the growth of the pollen-tube is quite 
rapid. As the tube elongates, both the body- and stalk-cells move forward 
