[RRITO-CONTRACTIL1TY IN PLANTS. 209 



65-70 seconds, is a revelation to us of the complexity of proto- 

 plasmic machinery. Drosera y then, like Dioncza, moves only 

 after a summation of at least two stimuli. 



I cannot sit down without acknowledging here my great 

 indebtedness to Mr. Oliver, of the Washington Botanic Garden, 

 for fine specimens of the rarer species experimented with, and 

 to my friend and former student, Mr. Aldrich Pennock, who 

 not only threw open his hot-houses for my use, but aided me 

 practically in many ways. 



