354 Miyake . — On the Development of the Sexual 
Picea :, and differs from Pinus , in which the division of the 
central cell takes place after pollination. 
Fig. i shows a pollen-grain in which the central cell is still 
undivided. Several stages of the division of the central cell 
are shown in Figs. 2-5. Figs. 1-6 are drawn from sections 
of the anthers, collected a few days before pollination. In 
the same anther, or even in a single section, I was often able 
to find out all the different stages figured here. The stalk- 
and generative cells are almost equal in size and structure 
when they are formed ; they usually contain several nucleoli 
(Fig. 6). The nucleus of the vegetative or tube-cell is oval 
or sub-spherical, and is situated very close to the free end of 
the generative cell. It contains usualty two or sometimes 
more nucleoli (Figs. 1-6). 
In the neighbourhood of Cornell University, Ithaca, N. Y., 
pollination takes place during about the second week in May. 
The dates varies somewhat by seasons. At the time of 
pollination, the female cone stands erect, the scales being 
divergent. It is about one-third or one-fourth the length of 
the mature cone. After about a week or ten days, the scales 
are closed and the cone begins to droop downward. 
The germination of the pollen-grain seems to take place 
in a few days after pollination. Soon after the formation of 
the pollen-tube, the tube-nucleus, which has usually a single 
nucleolus about this time, moves down towards the tip of the 
tube (Figs. 9, 10). Both the generative and stalk-cells continue 
to increase in size (Figs. 7-10). The generative cell enlarges 
more rapidly, and its nucleus soon assumes a more or less 
spherical shape with a prominent nucleus ; its cytoplasm 
becomes dense and deeply staining (Figs. 9-1 1). The cyto- 
plasm of the stalk-cell on the contrary assumes a vacuolate 
character. Its nucleus grows but slightly, and one or more 
prominent nucleoli, which were observed in its early stage 
of development, are now replaced by one or several small 
granules ; sometimes one of the granules is slightly larger 
and seems to represent a true nucleolus (Figs. 7-1 1). 
In the meantime the stalk-cell is detached from the inner 
