2i6 Ferguson . — Development of the Pollen-tube and the 
University, 42!° North lat., during**the latter part of May or 
early in June. 
3. The pollen-grain germinates very soon after pollination, 
and the vegetative nucleus immediately passes into the tube. 
4. The division of the antheridial cell takes place in Pinas 
Strobus and P. austriaca before the beginning of winter. It 
is probable that this cell does not always divide at a definite 
time, but that in a given species the time during which it 
may divide extends over a considerable period. 
5- During the first season the pollen-tube grows very 
slowly, and it may be broad and irregular in outline or it 
may branch freely. 
6. Shortly before fertilization the generative cell, followed 
by the stalk-cell, moves into the pollen-tube. The stalk-cell 
soon passes the generative cell and takes up a position near 
the vegetative nucleus. These changes and those immediately 
following are frequently much obscured by the presence in 
the pollen-tube of large quantities of starch. 
7. The generative cell, as the other cells of the pollen-grain, 
is never limited by a well-defined cell-wall, and consists at 
the time of its division of an irregular protoplasmic body, in 
the upper part of which the nucleus lies. 
8. In the division of the generative nucleus the spindle is 
extranuclear and unipolar in origin. 
The formation of the spindle indicates that the cytoplasmic 
network and the nuclear reticulum have essentially the same 
structure, and the spindle-fibres are apparently formed by 
a transformation of both. 
The nuclear membrane persists along the upper part of 
the nucleus until the early stages in the formation of the 
daughter-nuclei. 
This division takes place a little more than a year after 
pollination and from a week to ten days before fertilization, 
about thirteen months elapsing between pollination and 
fertilization. 
9. Two sperm-cells are never formed, but the sperm-nuclei 
remain surrounded by a common mass of cytoplasm. An 
