30 
FRED. ELFVING. 
a lengthening out whereby the large nucleus visibly dimin- 
ishes in volume. 
Bromus erectus corresponds in many particulars with 
Andropogon. The original cell-nucleus has often as many as 
four nucleoli. The two daughter-cells have often more. 
Division takes place in this species tolerably late, as 
seems to be the case in most of the Graminese, in this case 
when the ’anther is about a centimeter in length. The 
vegetative cell, which is also here formed diametrically 
opposite to the orifice in the extine (figs. 61 — 63), divides itself, 
not immediately, as in the case of the last-named plant, but 
after the nucleolus is resorbed, first loosens itself away 
from the extine and now appears free in the surrounding 
plasm in which it sooner or later assumes a somewhat elon- 
gated form (figs. 64, 65). Then it becomes hidden by a 
copious mass of starch grains I have only once seen the 
division into two of the vegetative nucleus in the uninjured 
Pollen-body (fig. 66), it is, oii the other hand, very easy 
when the Pollen-bodies are placed in a 5 per cent, sugar 
solution, to find conditions like those in figure 67, where the 
vegetative cell has become divided into two still attached 
cells, forming a sickle-shaped body. The two vegetative nu- 
clei are alike oval, and without any nucleolus. Later on they 
become considerably elongated, together with their surround- 
ing cells, which are often found in the crushed-out contents 
hanging on by their ends, the nuclei being then often crum- 
pled up ; the nucleus of the larger cell with its larger nu- 
cleolus being still unaltered (fig. 68). At the last even 
this nucleolus becomes dissolved, whereupon the nucleus 
stretches and curves itself, so that finally it is not to he dis- 
tinguished from the two vegetative nuclei, the surrounding 
protoplasm of which has meanwhile disappeared (fig. 69). 
In Butomus umbellatm , as in all the Liliacese, the vegeta- 
tive cell is formed directly opposite the opening in the extine, 
and somewhat late, namely, just before the buds are un- 
folded (fig. 75). The Pollen-body may remain in this state 
until the formation of the Pollen-tubes ; a division of the 
vegetative nucleus into two generally takes place, however, 
either when it is still enclosed in the vegetative cell (fig. 76), 
or after the partition wall is absorbed. Lastly, these two 
vegetative nuclei are small and roundish, with an indistinct 
nucleolus ; they are more deeply coloured by carmine than 
the nucleus of the large cell, which preserves its nucleolus 
a long time. 
Tubes were formed, but rather sparsely, in a solution of 
sugar, 5 per cent, strong, after a space of twenty to thirty 
