102 Wisconsin Academy of Sciences, Arts and Letters. 
leaf cells of Isoetes , 23 Later, during the processes of nuclear 
division in the spore mother-cells of Marsilia, as has been de¬ 
scribed, the starch grains undergo definite and specific translo¬ 
cations ; but these translocations are conspicuously different 
from those of the starch grains in young vegetative cells of 
Isoetes. This difference is at least partly due to the fact that 
in these cells of Isoetes the starch grains are confined to the 
interior of the “polar structure/’ and hence necessarily change 
their position as its position changes. The cells of Marsilia 
apparently do not possess a structure like the “polar struc¬ 
ture” of Isoetes. It is a striking fact that in Marsilia the 
often numerous starch grains, although as far as apparent not 
enclosed in any kind of an enveloping membrane, remain fairly 
closely packed in a single group from soon after the time of 
their first appearance in the cell until the completion of the 
second division; and we have in the specific changes of posi¬ 
tion and form which this group of starch grains undergoes an 
interesting point of attack upon the problem of the forces oper¬ 
ating in the cell during nuclear division. Starch grains, how¬ 
ever, do not universally show in their position and movements 
a marked effect of the forces operating in the cell during nu¬ 
clear division. The figures of Gregoire and Berghs for the 
early divisions in the germinating spore and in the spore 
mother-cells of Pellia epiphylla 24: are of interest in this connec¬ 
tion. There the starch grains are apparently scattered quite 
irregularly throughout the cytoplasm (not, however, through 
the karyokinetic figure). 
Contrary to what might be expected, the polar organization 
of the spore mother-cells of Marsilia, which is so conspicuous 
during the earlier stages, seems to have quite disappeared at 
about the time when the nuclear membrane breaks down, or at 
any rate it seems to find no expression in the arrangement of the 
spindle fibers just preceding the formation of the bipolar spin- 
23 Marquette, W. : Manifestations of polarity in plant cells which 
apparently are without centrosomes. ( Beih . bot. Centralbl ., xxi : 281. 
1907). 
24 Gregoire, V., and Berghs, J.: La figure aehromatique dans le Pel - 
Ua epiphylla. La Cellule, xxi : 193. 1904. 
