366 Miyake. — On the Development of the Sexual 
cytoplasm being very dense and finely granular, while the 
stalk-cell has a smaller nucleus and very vacuolate cytoplasm. 
4. About two weeks, or a little more after pollination, the 
generative cell followed by the stalk-cell moves down into the 
pollen-tube. The stalk-cell soon passes the generative cell 
and attaches itself to the lower side of the latter. 
5. The generative cell, after passing into the pollen-tube, 
is more or less elongated and somewhat irregular in its 
outline. It has no well-defined cell- wall, and the nucleus 
occupies at the time of its division the upper part of the 
dense protoplasmic body. 
6. The division of the generative cell has not been followed 
in detail. The process seems to be very similar to that 
of Pinus , as studied by Miss Ferguson. The cell-plate 
formed at the equator of the spindle later disappears, and 
two sperm-nuclei, which are unequal in size, remain surrounded 
by a common mass of cytoplasm. 
7. The sperm-nuclei, which are separated by a considerable 
distance when they are formed, soon come to lie together 
in the uppermost part of their cytoplasm, and early attain 
their full size, the lower one being always larger. 
8. The archegonium usually originates as a single super- 
ficial cell in the micropylar end of the female prothallium. 
Very early in its development it divides into two cells ; 
the upper smaller one forms the mother-cell of the neck 
and the lower larger one develops into the egg-cell. 
9. The number of archegonia in each prothallium varies 
from two to seven, the most usual number being four; three 
and five are the next common numbers ; six is less common, 
while two and seven are extremely rare. 
10. The central cell is at first very vacuolate, and its 
nucleus always remains close beneath the neck-cells. Later, 
its protoplasmic contents gradually increase, and the vacuoles 
begin to disappear. When the central cell is fully developed 
and its nucleus is ready for division, the number and size 
of the vacuoles become very much decreased, while a few 
proteid-vacuoles begin to appear in the cytoplasm. 
