204 Ferguson . — Development of the Pollen-tube and the 
after this the generative nucleus is again observed at the 
uppermost part of its cytoplasm (Figs. 21 and 22 ). 
During its passage into the tube, the generative cell 
increases much in size ; it has no definite cell- wall, and its 
cytoplasm forms a large, irregular tongue about the nucleus. 
This cytoplasm in no way suggests the alveolar structure of 
Biitschli (’94), but is distinctly reticular, differing in appear- 
ance from the nuclear net only by its greater delicacy. This 
is shown more clearly at a somewhat later stage. 
The vegetative and generative nuclei are now very similar 
in structure, though each is sufficiently characteristic to be 
readily recognized by one who is familiar with them. The 
vegetative nucleus has one large, usually homogeneously 
staining nucleolus, rarely one or more smaller nucleoli, and 
it is furnished with a rather scanty, delicate reticulum which 
is apparently poor in chromatin. Either it is in a state of 
more or less collapse, or it is very hard to fix at this period, 
for its outline is as a rule quite irregular. The generative 
nucleus has one large, hollow or vacuolate nucleolus, and 
commonly two smaller ones ; its reticulum, though more 
abundant than that of the vegetative nucleus, is still delicate 
and often shows a weak reaction to nuclear stains. The 
stalk-nucleus has a very decided individuality which it 
maintains throughout its entire history. It bears a strong 
resemblance from the first to the nuclei of the nucellar tissue, 
rarely, if ever, contains a true nucleolus, and its close-meshed 
reticulum is conspicuous for its comparatively large net-knots 
or karyosomes. 
Division of the Generative Nucleus. 
Dixon (’95) describes this division in Pinus sylvestris as 
taking place about a month before fertilization , while the 
generative cell is still within the pollen-grain ; and Coulter 
(’97) states, as already mentioned, that in his study of Pinus 
Laricio he has been able to confirm Dixon’s observations. 
At this time, as pointed out by Dixon, the nuclear and 
cytological phenomena are very greatly obscured by the 
