Notes. 
421 
difference being about 7-10 minutes, and with very strong light the 
movement is slower, showing that the optimum strength of stimulus 
has been surpassed. But the table also shows that a shorter initial 
stimulus than that required in the case of diffuse light was competent 
to produce the full effect. A change in the rate of turning similar to 
that observed in the experiments of series 1 occurs also here, and it 
is shown in Table II ; the controls also bear this out. 
The effect of different gases was also tried. Mesocarpus placed 
in hydrogen and exposed to continuous diffused light turned in the 
normal time. Some filaments were also placed in hydrogen and the 
dark for 50 minutes. On exposure to light, while still in hydrogen, 
these also turned in response to the stimulus in the normal time. 
Carbon dioxide acts as a complete anaesthetic, no movement taking 
place after an exposure for an hour to good diffused light. 
The appearance of the protoplasm in the cell when examined with 
a high power does not appear to alter during the process of turning. 
Slight staining with dahlia was tried, but this did not reveal anything 
further. 
The protoplasm is rather granular, and the granules perform a slow 
streaming movement along the cell-walls, very much after the manner 
of the circulation in Spirogyra. 
FRANCIS J. LEWIS. 
Botanical Laboratory, 
Royal College of Science, London. 
