345 
Centrifugal Force tip on the Cell. 
and its inclusions. In cells exposed to a temperature of 2° C 
in the cold house, twelve to twenty hours were often required 
for a complete redistribution. The time varied, of course, in 
cells of different parts of the same leaf. In the smaller ones 
near the tip, where displacement is less easily brought about, 
recovery takes place more quickly under whatever conditions 
may prevail in which protoplasmic activity is possible. 
VALLISNERIA. 
Longitudinal sections of leaves were used for experimenta- 
tion. Vallisneria proved to be a less favourable object for this 
study than the plants already mentioned. Even after a longer 
duration of centrifugal action, only a part of the chlorophyll 
was thrown into the lower end of the cell. On immediate 
examination after two hours of centrifugal action, a very 
decided movement was to be seen in many cells, both chloro- 
plasts and starch-grains being carried along in the cytoplasmic 
stream. Many chloroplasts, * were,, however, collected into 
larger and smaller clusters. Some of these clusters were 
thrown into the end of the cell, where they remained for 
a time, while others lay stationary along the sides of the cell. 
In a short time the chloroplasts became more evenly dis- 
tributed, those aggregated into clusters separating from one 
another. It seemed that in these cells the movement of the 
protoplasm was not brought to a standstill by the centrifugal 
action. Soon after the preparations had been removed from the 
centrifuge, the protoplasm began to rotate in many cells in 
whi'ch no movement was perceived at first, and it is reasonable 
to suppose that the motion had been inhibited in such cells. 
Even in many cells in which no protoplasmic movement was 
noticeable when the experiment was begun, the chloroplasts 
were displaced in part only. 
Since it seemed that the movement of the protoplasm 
interfered somewhat with the displacement of the cell-contents, 
an attempt was made to determine, if possible, in what 
measure the movement hindered the dislocation of the chloro- 
