296 Schively — Contributions to the Life History of 



plant which has been circumnutating well, though perhaps 

 slowly, will cause it to become stationary and remain so 

 for a time. The last two statements have not been put to 

 the test of many experiments. 



Some of this work was done during the winter in the 

 greenhouse. Difficulties were encountered in the varying 

 temperature and moisture of the greenhouse, also the 

 supply of fresh air ; but on the whole, results were very 

 satisfactory. Experiments were continued during May, 

 June and July, when the greenhouse was not artificially 

 heated. Out of doors, even a slight wind was a disturbing 

 factor. The greenhouse being well ventilated, the tem- 

 perature varied little from that outside. As the glass above 

 was very lightly white-washed, the shade produced a con- 

 dition similar to that in which the plants normally grow. 



Specimens under observation were placed as close as 

 possible (without touching) to the glass upon which records 

 were made. No special effort was made to obtain a con- 

 tinuous path traversed by the plant, though all records are 

 fairly accurate. The time in which the revolution might 

 be completed was the information desired. Few observa- 

 tions were made as to the number of internodes circumnu- 

 tating at one time. Two or three seem to be in activity at 

 the same time; no difference in the rates could be distin- 

 guished; the movement seemed uniform. 



Plants under eight inches exhibited slow, irregular 

 movements, rarely forming a circle. When nine to ten 

 inches long the curving of the tip became more evident, 

 and from this time on, as the twining inclination increased, 

 the path described became circular. The rate of elongation 

 is rapid — from one to two inches a day. 



There is a certain marked periodicity. Beginning 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 there is 

 a gradual decrease in the rate, until several hours after 

 midnight. The maximum period may be much extended, 



