Fertilization in Pinus Strobus. 469 
At the time of fertilization, an opening is formed in the 
apex of the pollen-tube, and the cells of the male gameto- 
phyte which still persist, together with a portion of the 
cytoplasm and some of the starch of the pollen-tube, pass into 
the cytoplasm of the egg. 
The larger sperm-nucleus escapes from the protoplasm of 
the sperm-cell and moves directly toward the egg-nucleus ; 
the other nuclei from the pollen-tube may persist, in a modified 
form, in the upper part of the archegonium until the eight- 
celled stage of the proembryo ; but the cytoplasm of the 
sperm-cell fuses at once with that of the oosphere. The stalk- 
cell gradually disintegrates and blends with the egg-cytoplasm. 
The vegetative nucleus and the smaller sperm-nucleus may 
share the fate of the stalk-cell, but, during the second division 
following fertilization, they not infrequently give rise to mitotic 
figures. The smaller sperm-nucleus, then, may pass through 
a slow process of disintegration, it may divide amitotically, or 
it may give rise to a karyokinetic figure of more or less 
definiteness. 
There is no apparent change in the diameter of the sperm- 
nucleus after its entrance into the oosphere. At the time of 
conjugation, the egg-nucleus is several times larger than the 
sperm-nucleus, and the sperm-nucleus does not increase in 
size after its contact with the egg-nucleus. The inequality in 
the size of the sexual nuclei may be due to the difference 
in the size of their cells. But if, as has been suggested, the 
egg-nucleus functions as a manufacturer of nutritive material, 
may we not find in this activity a feasible explanation of its 
greater size? The conjugating nuclei always dissimilar in 
size may, or may not, be similar in structure. 
The egg-nucleus becomes slightly concave on the side 
nearest to the approaching sperm-nucleus. This nucleus 
embeds itself in the side of the egg-nucleus but does not 
penetrate its membrane. There is never any fusion, as 
ordinarily understood, of these two nuclei. A chromatic spirem 
arises, and a prominent achromatic reticulum becomes ap- 
parent in each nucleus. Soon afterwards the nuclear mem- 
