362 Miyake . — On the Development of the Sexual 
Fertilization. 
The date of fertilization varies for the same and different 
trees much as pollination does. In 1901 the earliest date for 
fertilization was June 15, while in the same tree the conjugat- 
ing nuclei were observed as early as June 7 in the following 
year, the process being apparently most active on the 9th or 
10th. The difference may largely be ascribed to the unusually 
early season in 1902, and the condition in 1901 may probably 
represent that of the normal year. Generally speaking, we 
may say that in the neighbourhood of Cornell University the 
fertilization of Picea excelsa takes place about the middle 
of *June. 
The egg seems to be fertilized about five days or a week 
after the formation of the ventral canal-cell. The pollen-tube 
reaches the egg by penetrating the neck of the archegonium, 
and nearly the whole contents of the lower part of the tube, 
including the two sperm-nuclei, pass into the egg. 
In the mature egg which is ready for fertilization, a vacuole 
was often observed just beneath the neck. Sometimes a few 
smaller vacuoles may also be present near the larger one. 
Miss Ferguson’s suggestion about the similar vacuole in Pinus 
Strobus is very instructive ; she says that ‘ this opening in the 
cytoplasm represents the last act of the egg in its preparation 
for the reception of the sperm-nucleus.’ But I am not quite 
ready to accept her interpretation without making more 
careful and extensive observations. The vacuole was some- 
times observed in the egg after fertilization (Figs. 51, 52). 
The larger sperm-nucleus immediately moves down towards 
the nucleus of the egg. There is no evidence that the sperm- 
nucleus increases in size after entering, as was supposed to be 
the case by some investigators (Coulter ’ 97 ). The sperm- 
nucleus is much smaller than the one figured by Strasburger 
(’84 a), being about one-third the diameter of the egg-nucleus. 
The sperm-nucleus first comes in contact with the egg- 
nucleus and soon begins to press itself against the latter. 
Thus the sperm-nucleus becomes more or less imbedded 
