34i 
Centrifugal Force upon the Cell. 
of a large number of Phanerogamic species, from widely 
different families were used, with results varying only in 
minor details. Those of Urtica , Momordica and Cucurbit a , 
which seemed more favourable for this study, merit some 
special mention. 
Sections of the leaf or petiole bearing hairs of suitable 
age were fastened upon the slide under a cover-glass in the 
same way as the algal filaments. Hairs of Urtica and 
Momordica are quite hardy, the cells living often for a week 
or ten days after subjection to a centrifugal force of 1820^* 
for one and a half to two hours ; though of course there are 
always cells that seem to be seriously injured or killed out- 
right either by handling or by the centrifugal action. 
The cell-contents of hairs of Momordica possess about the 
same orientation as in Tradescantia , except perhaps that 
a greater number of plasmic strands traverse the cell-cavity 
or vacuole. 
Centrifugal action lasting for one hour and a half dis- 
places nucleus, chloroplasts, and much of the cytoplasm with 
all conspicuous inclusions, massing them in the lower end 
of the cell. As in Tradescantia , a number of the larger 
plasmic strands persist. The streaming movement of the 
cytoplasm may not have been entirely stopped by the 
action of the centrifugal force, for it was seen immediately 
the preparation was taken from the centrifugal machine, which 
required from five to seven minutes. It is possible, however, 
that the movement may begin again within that time. 
The contents of the cells redistribute themselves in a 
relatively short time, usually less, than twenty-four hours. It 
sometimes happens that a portion of the cell-contents con- 
sisting of dead or inert particles will remain in the lower end 
of the cell separate, and perhaps entirely cut off, from the 
actively circulating cytoplasm. 
In the long pointed hairs of Urtica , when the contents are 
forced into the attenuated end of the cell, the nucleus 
especially, which seems wedged in between the walls, finds 
more difficulty in extricating itself. At the end of centrifugal 
A a 
