Circumnutation of Some Flowering Plants. 71 



there is a gradual decrease in the rate, until several hours after 

 midnight. The maximum period may be much extended, 

 beginning earlier and continuing until 4 or perhaps 4.30 p. m., 

 if the day is very hot." From the tables compiled by the 

 writer, the following comparison of four-hour periods is 

 obtained. The agreement of these statistics drawn from five 

 species of plant, with the statement above quoted need merely 

 be noted. 



Between the hours were performed 



8 — 12 a. m II circumnutations. 



9 — I p. m 12 " 



10 — 2 " II " 



JI— 3 " 16 



i^— 4 " 19 



I-- 5 " 23 



2— 6 " 18 



When the experiments were begun, it was thought that 

 under our comparatively bright sky and warmer temperatures, 

 as contrasted with the atmo.spheric surroundings of England, 

 circumnutations might be performed more rapidly than in the 

 shortest time-limits given by Darwin. Subjoined is a compari- 

 son of the two sets of results : 



At Darwin's Home. 



Phaseolus. (Greenhouse, May 2) i h. 55 m. 



Humulus. (" Hot weather " ) 2 h. 8 m. 



Convolvulus I h. 42 m. 



Lonicera. (House, April 3) 7 h. 30 m. 



Wisteria. May 16 2 h. 5 m. 



At University of Pennsylvania. 



Pliaseoliis. (Greenhouse, April 5) i h. 20 m. 



July 18 1 h. 



Humulus. " February 9 1 h, 5 m. 



Convolvulus. " March 25 57 ni. 



Lonicera. April 5 2 h. 48 m. 



" August 15 I h. 43 m. 



Wisteria. July II 2 h. 



