26 



Bsihcr Pearl Hens el 



EPHEMERAL TYPES 



Only three ephemeral, day blooming flowers were experi- 

 mented with: the morning- glory {Ipomoca purpurea), the com- 

 mon flax (Liniim nsifatissii)iniii), and the yellow wood sorrel 

 (Oxalis stricta) ; the other two wer^ night bloomers, the evening 

 primrose (Pachyloplius eaespitosiis) and the four o'clock (Mira- 

 bilis jalapa). 



Expcrinients with Ipomoca purpurea. Tpomoea opens from 

 5:00 to 6:00 A.M. and closes as early as 10:00 or ti:oo a.m. 

 when it is quite warm. (All experiments were performed in the 

 greenhouse.) Generally, however, closing occurs between i :oo 

 and 3:00 P.M. Contrary to the results with the dandelion, it was 

 always possible to keep the flowers open for a considerable time 

 (24 hours at least) beyond the normal, by placing the plant in 

 a temperature as low as 3 to 4° C. ; also to close the flowers 

 earlier than their time by increased temperature (28 to 32° C.) 

 with dry air or with water vapor introduced. On the other hand, 

 heat does not work here as a direct stimulus, but rather only 

 to hasten the growth processes. The following tables show how 

 clo.sing is hindered in temperatures lower than the normal: 



216 



