Chap. I. 



CUCUELITA. 



43 



10'35p.m. 



6° S8'a.m. \ 



18^ 



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. P'g- ^O- 



In order to ascertain more ac- A 



curately the nature of these move- j i e<>is'p.7B. 



ments, the hypocotyl of a seedling, j \ iiw 



with its cotyledons weU expanded, 

 vas secured to a Uttlo 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 17i° to 18° 0. (63° to 

 65° P.), Had the temperature been 

 higher and the Mght brighter, the 

 movements would probably have 

 been greater. On July 11th (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 evening ; 

 and this was 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 (Cucurbitacese). — Two seedlings had opened 





12 " 

 , a'S'a.m. 

 \1 14*1 



Lagcnaria vulgaris: circumnu- 

 tation of a cotyledon, 1^ 

 inch in lengtli, apex only 4| 

 inches from the vertical glass, 

 on which its movements were 

 traced from 7.35 A.M. July 

 11th to 9.5 A.M. on the 14th. 

 Figure liere given reduced 

 to one-third of original scale. 



