Pinus silvestris . 
23 
(Stielzelle) next the wall of the pollen-grain and a larger 
body-cell. Where the cell-group is, in this way, composed of 
more than two cells, Prof. Strasburger found that it was already 
formed in the anther ; whereas in others (e. g. Taxus , Cupres- 
sus, & c.) the pollen-grain reached the nucellus before any cell- 
division took place within it. 
As the result of these divisions, which have taken place in 
the pollen-grain either while it is still in the anther, or after it 
has been transported to the nucellus, there are in it three cells ; 
the large cell which grows out to form the pollen-tube, the 
small stalk-cell, and the body-cell, which by a subsequent 
division gives rise to two cells, which contain the male sexual 
nuclei. Besides these cells, there are in Larix and most of 
the Coniferae, in which several prothallium-cells are formed, 
the remains of these prothallium-cells persisting as scarcely 
perceptible clefts in the wall of the pollen-grain at the base of 
the stalk-cell. 
It was by tracing the subsequent behaviour of this cell- 
complex formed within the pollen of Taxus, that Belajeff 
showed that the nucleus of the pollen-tube was not a sexual 
nucleus, but that fertilization was effected by the nucleus of 
one of the cells arising by the division of the body-cell. 
According to the further researches of Belajeff and Prof. 
Strasburger, after the pollen-tube is formed and its nucleus 
has moved into it, the body-cell breaks free in the pollen-grain 
and wanders into the tube following the nucleus of the tube. 
This breaking free of the body-cell appears to be facilitated 
by the fact that the stalk-cell relinquishes its independence 
and through the rupture in its wall, left by the breaking away 
of the body-cell, its nucleus escapes and follows the body-cell 
into the pollen-tube. The nucleus of the stalk-cell soon over- 
takes the body-cell and, passing it by, comes into a position 
close to the nucleus of the pollen-tube. In all cases so far 
examined, the body-cell divides into two daughter-cells either 
while yet in the pollen-grain or after it has passed into the 
pollen-tube. An example of the first case is Larix europaea , 
and of the second are Taxus baccata and Juniper us virginiana. 
