12 BOTANICAL GAZETTE. [ Jan. 
utes, at most five or ten, the swelled up sufficiently to 
show their apalatte and usually e two nuclei became plainly 
visible. Figures 1 oe show some of ete most common positions. 
In the os adie e of these nuclei we use that of Strasburger 
in his Neue Unter suelnnge followed by Barnes in the paper al- 
ready referred to, exactly the opposite of that of at ee 
in his Botanisches Pr -acticum, and Sachs in his Text-book.° 
generative nucleus is a thick, worm-like filament, tapering ms 
both ends, and always more or less coile ts appearance is 
exactly that gured by Bernimoulin in his studies’ in the division 
of the nucleus in the pollen-spore mother-cells of the same spe- 
cies. The vegetative nucleus is round or oval, of much smaller 
size, and some of its positions with reference to the generative 
nucleus are shown in figures 1-4. In some cases, as in figure 4, 
the generative nucleus is seen almost to encircle the contents of 
the pollen-spore. In figures 5 and 6 is seen the small cell cut off 
from the larger ¢ one, containing the generative nucleus, and form- 
ing the generative cell. The generative nucleus always lies 
against the intine wall, and its apparent central position in some 
cases, as in figures 1 and 3, is explained by the fact that it is ly- 
ing against the upper or ‘lower wall in the figure. The wall 
which cuts off the generative cell seems to be simply an ectoplas- 
mic layer of protoplasm,*° and not in any case cellulose. That 
this layer is often difficult to demonstrate seems to be due both 
to the fact that the generative nucleus almost entirely fills its cell, 
and that it is so transparent that only an exceptional position 
will bring it into view. 
Usually within fifteen minutes, or at most half an hour, the 
pollen-tube can Le seen developing from the larger or vegetative 
cell. It breaks through the extine at one end of the spore, and 
the broken edges of the extine can be seen turning back from the 
emerging tube, figure 7. The generative nucleus retains its po- 
sition until the pollen-tube is of considerable length, when it 
e seen shifting its position towards the side of the pollen- 
vets from which the tube is ee (figure 8). The stream- 
in the nuclei themselves. The fact that the nucleus of the vege- 
tative (large) cell invariably remains towards the further end of 
the spore until the generative nucleus passes into the tube, seems 
® Second English edit., p. 5 
7 Note sur hy Division des Sirus dans le Tradescantia Virginica. Bull. Soe. Roy. 
bot. Belgique, t. xxiii 
8 Sachs’ Text-book, 2d English ed., p. 583. 
