2 2 Dixon. — Fertilization of 
of the cells of the cell-group formed within the pollen-grain. 
This fact, which was established by Belajefif for Taxus baccata , 
was shown to be generally true for the Gymnosperms by Prof. 
Strasburger \ 
The misunderstanding with regard to the nature of the 
cell-group of the pollen arose from the fact that in all artificial 
cultures the cells composing it remain in the position where 
they are formed, while the nucleus of the pollen-tube approaches 
the end of the tube. Accordingly it was naturally supposed 
that the cell-group could not contain sexual nuclei as, in the 
cultures, its nuclei never left the pollen-grain and consequently 
could not reach the oosphere ; whereas the nucleus of the 
pollen-tube, by wandering into the tube, would naturally be 
in a position to unite with the female nucleus. And hence 
it was regarded as the sexual nucleus. Belajeff found however, 
that, when on the nucellus, the cells of the included cell-group 
of the pollen of Gymnosperms behave quite differently. 
Prof. Strasburger found that in some cases (e. g. Larix 
europaea) several divisions had already taken place in the 
pollen-grain before it had reached the nucellus. In this 
instance the undivided pollen-grain divides while still in the 
anther into a large and a small cell 2 . The latter is lens- 
shaped and applies itself closely to the wall of the pollen- 
grain. Its contents soon become highly refractive and it 
flattens itself against the wall of the pollen-grain. About this 
time another cell is cut off from the large cell and it applies 
itself against the first cell, which is already flattened against 
the wall. This second cell suffers the same fate as the first, 
and then a third much more strongly arched cell is cut off 
from the large cell. This third cell is so placed that it covers 
over the first two cells, which by this time are completely 
flattened out and appear as mere cracks in the wall of the 
pollen-grain. Unlike the two first-formed cells, this cell does 
not flatten out, but divides into two, a small stalk-cell 
1 Ueber das Verhalten des Pollens und die Befruchtungsvorgange bei den 
Gymnospermen. Jena, 1892. Belajeff also records further observations of his own 
in Ber. der Deut. Bot. Ges., April 26, 1893. 
2 Befruchtungsvorgang bei den Phanerogamen. 1884, p. 2. 
