70 Simons—Comparative Studies on the Rate of 
and leaves. Darwin worked on this species in a greenhouse 
from May 13 till May 25, and obtained as his shortest time, 
2 hours 5 minutes, with an average of 2 hours 501% minutes. 
By taking advantage of every fresh sprout as it began to reach 
for a support, the results appended were obtained. 
Growing in a protected corner of the garden was another 
Wisteria, with long, strong stems, of which three were unsup- 
ported. On August 18, these were gently secured to stakes, 
two of them hanging just as on the vine, being secured at one 
point to a stick to insure against wind interference, the third 
being tied upright with about nine inches free. This began 
its twisting in that position, but gradually became horizontal 
from the point of attachment. Apparatus for marking was 
set up and the following results obtained. All the stems were 
exposed to direct sunlight except for a short time, when they 
passed through an arc shaded by the plant itself. 
The shortest time obtained was 2 hours, the average of all 
observations 2 hours 1534 minutes. 
As to the time of day when circumnutation is most rapid, 
the following diagram was made from the foregoing records 
of the five species examined. The temperature recorded for 
a circumnutation represents the average for the hours between 
which the circle was made. The temperature records are 
suggestive, those during the shortest circumnutations ranging 
from. 25..5°C. to 36:5 C:; of the longest, 15.5°C. to 30,5. 
From the table it will be noticed that of the 31 quick twin- 
ings, 22 are in the afternoon. Looking at the list of long 
circumnutations 8 of 18 are in the afternoon. But a more 
detailed analysis brings out some interesting results, that corre- 
spond very closely with those given by Dr. Schively in the 
paper already cited (pp. 296-97). The following statement is 
there made regarding periodicity of circumnutation. ‘“ Begin- 
ning with the early hours of morning, there is a gradual 
acceleration until 11 or 11.30 a.m. The greatest rapidity 
occurs from this time until 2 or even 3 p.m. After that time 
