356 Mot tier. — The Effect of 
the rate of growth as influenced by the action of centrifugal 
force. 
Root-tips were fixed at subsequent intervals of six, eight, 
twenty, and twenty-four hours. In six or eight hours the 
displaced contents had become in a measure redistributed 
except in the long narrow cells of the plerome, and at the 
end of twenty or twenty-four hours no signs of a displacement 
were evident. But, if the nucleolus had been forced out of its 
nucleus, these two bodies were found lying separately in the 
cytoplasm, sometimes at considerable distances from each 
other. The nucleolus did not re-enter the nucleus even when 
a connexion remained between them as in Fig. 13. The 
enucleolated nuclei were often irregular in shape and not 
infrequently showed signs of disorganization. 
All attempts to eject the nucleolus in cells of the various 
trichomes, &c., proved futile. Either the resistance offered by 
the cytoplasm to the movement of the nucleus was too feeble, or 
the nucleolus was too light to admit of its ejection by means 
of the centrifugal force employed. Negative results were also 
obtained with trichomes from the leaves of Pinguicula , whose 
nuclei contain large crystals. Neither crystals nor nucleoli 
were ejected. 
It was thought that sharp-pointed raphides of such plants 
as Agave mexicana might be made to pierce the cellulose- 
membrane. In Agave mexicana and others the raphides 
occur in cells containing mucilage, and, although the entire 
bundle is thrown into the end of the cell so that the sharp 
ends of the raphides touch the cell-membrane, yet in no case 
could they be seen to penetrate the wall in the least. After 
the operation the raphides moved back to their former 
position in the cell. 
Concluding Remarks. 
One of the great tasks of the physiologist, and perhaps 
that which overshadows all others in theoretical importance, 
is to know what cells can do under any and all conditions 
