Organs and Fertilization in Picea excels a. 365 
the superficial layer of the prothallium. In one of them the 
ventral canal-cell was found at the side of the egg, instead of 
the top (Fig. 61). Two archegonia, lying one above the other, 
were observed several times, and both archegonia were found 
to be somewhat smaller than the normal one. The lower 
archegonium, which is usually larger than the upper one, 
has no neck-cells, but the ventral canal-cell is usually formed. 
Fig. 62 shows a double archegonium, in both parts of which 
the central cell is still undivided. The division of the central 
cell does not always take place simultaneously. In Fig. 63 
the nucleus of the lower archegonium is dividing while that of 
the upper one remains still undivided. A later stage is shown 
in Fig. 6 4 ; the nuclei of both archegonia are already divided 
and each egg-nucleus is approaching the centre of the egg. 
The disorganizing ventral canal-cell, which is somewhat 
lenticular in shape, is seen on the upper left-hand corner 
of the lower archegonium ; that of the upper archegonium 
is found in another section, and is not sketched here. 
Summary. 
t. The mature pollen-grain contains the large tube-cell, 
two smaller generative and stalk-cells, besides two disinte- 
grating prothallial cells. The third prothallial cell or central 
cell divides into the stalk and generative cells before pol- 
lination, as already described by Strasburger. This division 
seems to take place within a few days before pollination. 
2. Pollination takes place, in the vicinity of Ithaca, N.Y., 
about the second week in May. The pollen-grain germi- 
nates in a few days after pollination. 
3. Soon after the formation of the pollen-tube, the tube- 
nucleus leaves the grain, and is found near the tip of the tube. 
The generative and stalk-cells, which are nearly equal in size 
and structure when first formed, begin to increase in size, and 
soon the two cells present very different appearances. The 
generative cell enlarges more rapidly, and its nucleus assumes 
a more or less spherical shape with a prominent nucleolus, its 
