42 CIRCUMNUTATION OF SEEDLINGS. CHAP. I. 



cotyledon fell; it then rose rapidly till 9 P.M., then very 

 gradually till 3 A.M. February 19th, after which hour it sank 

 gradually till 4.30 P.M. ; but the downward movement was inter- 

 rupted by one slight rise or oscillation about 1.30 P.M. After 

 4.30 P.M. (19th) the cotyledon rose till 1 A.M. (in the night of 

 February 20th) and then sank very gradually till 9.30 A.M., 

 when our observations ceased. The amount of movement was 

 greater on the 18th than on the 19th or on the morning of 

 the 20th. 



Cucurbita aurantia. An arched hypocotyl was found buried a 

 little beneath the surface of the soil ; and in order to prevent it 

 straightening itself quickly, when relieved from the surrounding 

 pressure of the soil, the two legs of the arch were tied together. 

 The seed was then lightly covered with loose damp earth. A 

 filament with a bead at the end was affixed to the basal leg, the 

 movements of which were observed during two days in the 

 usual manner. On the first day the arch moved in a zigzag line 

 towards the side of the basal leg. On the next day, by which 

 time the dependent cotyledons had been dragged above the sur- 

 face of the soil, the tied arch changed its course greatly nine 

 times in the course of 14 h. It swept a large, extremely irre- 

 gular, circular figure, returning at night to nearly the same 

 spot whence it had started early in the morning. The line was 

 so strongly zigzag that it apparently represented five ellipses, with 

 their longer axes pointing in various directions. With respect 

 to the periodical movements of the cotyledons, those of several 

 young seedlings formed together at 4 P.M. an angle of about 60, 

 and at 10 P.M. their lower parts stood vertically and were in 

 contact ; their tips, however, as is usual in the genus, were per- 

 manently reflexed. These cotyledons, at 7 A.M. on the following 

 morning, were again well expanded. 



Layenaria vulgaris (var. miniature Bottle-gourd) (Cucurbi- 

 taceae). A seedling opened its cotyledons, the movements of 

 which were alone observed, slightly on June 27th, and closed 

 them at night: next day, at noon (28th), they included an 

 angle of 53, and at 10 P.M. they were in close contact,. so that 

 each had risen 261. At noon, on the 29th, they included an 

 angle of 118, and at 10 P.M. an angle of 54, so each had 

 risen 32. On the following day they were still more open, and 

 the nocturnal rise was greater, but the angles were not measured. 

 Two other seedlings were observed, and behaved during three 

 days in a closely similar manner. The cotyledons, therefore, 



