CHAP. 1. OUCUEBITA. 4] 



the other leg adjoiuing the radicle likewise circumnutated at an 

 equally early age. 



The movement of t!e same hypocotyl after it had become 

 straight and vertical, but with the cotyledons only partially 

 expanded, is shown in Fig. 29. The course pursued during 12 h. 

 apparently represents four and a half ellipses or ovals, with 

 the longer axis of the iirst at nearly right angles to that of the 

 others. The longer axes of all were oblique to a line joining 

 the opposite cotyledons. The actual extreme distance from 

 side to side over which the summit of the tall hypocotyl 

 passed in the course of 12 h. was ■ 28 of an inch. The original 

 figure was traced on a large scale, an.l from the obliquity of 

 the line of view t'le outer parts of the diagram are much 

 exaggerated. 



Cotyledons. — On two occasions the movements of the cotyle- 

 dons were traced on a vertical glass, and as the ascending and 

 descending lines did not quite coincide, very narrow ellipses 

 were formed; they therefore circumnutated. Whilst young 

 they rise vertically up at night, but their tips always remain 

 reflexed ; on the following morning they sink down again. With 

 a seedling kept in complete darkness they moved in the same 

 manner, for they sank from 8.45 a.m. to 4.30 p.m.; they then 

 began to rise and remained close together until 10 p.m., when 

 they were last observed. At 7 a.m. on the following morning 

 they were as much expanded as at any hour on the previous 

 day. The cotyledons of another young seedling, exposed to the 

 light, were fully open for the first time on a certain day, but 

 were found completely closed at 7 a.m. on the following morning. 

 They soon began to expand again, and continued doing so till 

 about 5 P.M. ; they then began to rise, and by 10.30 p.m. stood 

 vertically and were almost closed. At 7 a.m. on the third morn- 

 ing they were nearly vertical, and again expanded during the 

 day; on the fourth morning they were not closed, yet they 

 opened a little in the course of the day and rose a little on the 

 following night. By this time a minute true leaf had become 

 developed. Another seedling, still older, bearing a well-developed 

 leaf, had a sharp rigid filament af^xed to one of its cotyledons 

 (85 mm. in length), which recorded its own movements on 

 a revolving drum with smoked paper. The observations were 

 made in the hot-house, where the plant had lived, so that there 

 was no change in temperature or light. The record commenced 

 at 11 A.M. on February 18th; and fiom this hour till 3 p.m. the 



