CHAP. I. 



CUCUKBITA. 



1035f.m 



open more and more on each succeeding day, and rise each 

 night about 30 ; consequently during the first two nights of 

 their life they stand vertically and 

 come into contact. 



In order to ascertain more ac- 

 curately the nature of these move- 

 ments, the hypocotyl of a seedling, 

 with its cotyledons well expanded, 

 was secured to a little stick, and a 

 filament with triangles of paper 

 was affixed to one of the cotyledons. 

 The observations were made under 

 a rather dim skylight, and the 

 temperature during the whole time 

 was between 17 to 18 C. (63 to 

 65 F.). Had the temperature been 

 higher and the light brighter, the 

 movements would probably have 

 been greater. On July llth (see 

 Fig. 30), the cotyledon fell from 

 7.35 A.M. till 10 A.M. ; it then rose 

 (rapidly after 4 P.M.) till it stood 

 quite vertically at 8.40 P.M. During 

 the early morning of the next day 

 (12th) it fell, and continued to fall 

 till 8 A.M., after which hour it rose, 

 then fell, and again rose, so that by 

 10.35 P.M. it stood much higher than 

 it did in the morning, but was not 

 vertical as on the preceding night. 

 During the following early morn- 

 ing and whole day (13th) it fell and 

 circumnutated, but had not risen 

 when observed late in the evenirfg ; 

 and this wa& probably due to the 

 deficiency of heat or light, or of 

 both. "We thus see that the coty- 

 ledons became more widely open at 

 noon on each succeeding day ; and 

 that they rose considerably each night, though not acquiring 

 a vertical position, except during the first two nights. 



Cucumis dudaim (Cucurbitaceae). Two seedlings had opened 



Lagcnaria vulgaris : circumnu- 

 tation of a cotyledon, l 

 inch in length, apex only 4f 

 inches from the vertical glass, 

 on which its movements were 

 traced from 7.35 A.M. July 

 llth to 9.5 A.M. on the 14th. 

 Figure here given reduced 

 to one-third of original scale. 



