Marquette—Spore Mother-Cells of Marsilia . 83 
ning to divide. A tissue cell is subject to specific and different 
environmental conditions on its different sides, certain factors 
of which remain constant for at least considerable periods. With 
the free spore mother-cells it is otherwise. While the conditions 
are not the same in all directions in the spore sac, any part of 
a free spore mother-cell apparently is as likely to lie in a 
given position as any other; furthermore, there is some evi¬ 
dence that the spore mother-cell rotates more or less previous 
to and during division, so that, whatever differences there may 
be in the environment of a spore mother-cell, there are no 
fixed and specific differences with respect to the environment 
between different parts of the cell, as is the case with cells form¬ 
ing part of a tissue complex, and in this difference a possibility 
is provided for a difference in the method of formation and 
orientation of the karyokinetic figure in the two cases. 
In the following, I shall take up only the organization of 
the spore mother-cells and the processes of division occurring 
in them. I have concerned myself especially with the activi¬ 
ties of the cytoplasm. The points in Strasburger’s paper, 3 
which appeared when my work was practically completed, 
bearing on the problems taken up here will be considered as 
they come up. 
Shortly after their formation, the sixteen spore mother-cells 
of a spore sac each show an approximately centrally placed 
nucleus in a dense cytoplasm. The more solid constituents of 
the cytoplasm are closely packed and usually show no inclu¬ 
sions at this time. Nucleus and cell are of relatively small 
size as compared with later stages. A period of growth now 
sets in during which the size of the nucleus and cell increase 
greatly up to the time of synapsis. During this period 
of growth, specific and characteristic changes occur in the 
cytoplasm. At what is apparently a variable period in the 
growth of the spore mother-cell, starch grains make their ap¬ 
pearance in the cell. Just before they appear, the cytoplasmic 
strands, or lamellae, of the spore mother-cell are relatively 
coarse and of irregular outline. For the most part, these 
s-Strasburger, E.: Apogamie bei Marsilia. Flora, xcvii:123. 1907, 
