Division of the Generative N tic lens in Pines . 197 
in these plants, spermatozoids would be superfluous and are, 
in reality, not present. He added, however, that their place 
is taken by granular protoplasm and starch-grains which 
exercise the same fertilizing effect on the egg as do sperma- 
tozoids. In 1872 Strasburger detected two cells in the 
pollen-tube of several Gymnosperms, but considered that 
such cells were extremely rare in the Abietineae, as he had 
only once found one in this group. The shrunken remains 
of these cells were seen in the pollen-tube after fertilization. 
He thought that the pit of the pollen-tube remained closed, 
and that the exchange-substance was apparently communicated 
by a vacuole between the apex of the pollen-tube and the 
egg-nucleus. Six years later (78) he observed two nuclei in 
the pollen-tube of Pinus and Picea when the tube was just 
above the archegonium. According to his interpretation at 
that time, the nucleus in front was dissolved while the one 
behind entered the egg and fused with its nucleus. This 
was a great advance on his previous observations ; but he 
still conceived of the pollen-tube as remaining closed, and 
fancied that the protoplasmic contents passed through the 
membrane directly, while the starch was dissolved before its 
transmission into the egg. In the following year (79) he 
established the fact that it is the foremost of the two sperm- 
nuclei in the pollen-tube which becomes active in fertilization. 
Goroschankin (’83) saw the two sperm-nuclei pass into the 
egg in Pinus Pumilio , and he believed that both fused with 
its nucleus. Strasburger (’84) confirmed his observation as to 
the passage of the two sperm-nuclei from the pollen-tube 
into the egg, but pointed out that only the one in advance 
fuses with the egg nucleus. 
It was left for Belajeff (’91) to establish the true nature of the 
cell-complex found in the pollen-grain of the Gymnosperms. 
He demonstrated the fact that in Taxus baccata the large 
nucleus of the pollen-grain is the vegetative or pollen-tube 
nucleus, as in the Angiosperms, and that the sperm-nuclei 
arise by the division of one of the smaller cells of the pollen- 
grain. This smaller cell divides to form the stalk- and the 
