501 MODIFIED CIECUMNUTATION. Chap. X 



peduncles bend downwards, and this is due to epinasty; for 

 on two occasions when pots were laid horizontally, the sub- 

 peduncles assumed the same position relatively to the main 

 peduncle, as would have been the case if they had remained 

 upright; that is, each of them formed with it an angle of 

 sibout 40°. If they had been acted on by geotropism or aphelio- 

 tropism (for the plant was illuminated from above), they would 

 have directed themselves to the centre of the earth. A main 

 peduncle was secured to a stick in an upright position, and ono 

 of the upright sub-peduncles which had been observed ciroum- 

 nutating whilst the flower was expanded, continued to do so for 

 at least 24 h. after it had withered. It then began to bend 

 downwards, and after 36 h. pointed a little beneath the horizon. 

 A new figure was now begun (A, Fig. 188), and the sub-peduncle 

 was traced descending in a zigzag line from 7.20 p.m. on the i9th 

 to 9 A.M. on the 22nd. It now pointed almost perpendicularly 

 downwards, and the glass filament had to be removed and 

 fastened transversely across the base of the young capsule. 

 We expected that the sub-peduncle would have been motionless 

 in its new position ; but it continued slowly to swing, like a 

 pendulum, from side to side, that is, in a plane at right angles 

 to that in which it had descended. This circumnutating move- 

 ment was observed from 9 a.m. on 22nd to 9 a.m. 24th, as shown 

 at B in the diagram. We were not able to observe this par- 

 ticular sub-peduncle any longer ; but it would certainly have 

 gone on circumnutating until the capsule was nearly ripe (which 

 requires only a short time), and it would then have moved 

 upwards. 



The upward movement (0, Fig. 188) is effected in part by tha 

 whole sub-peduncle rising in the same manner as it had pre- 

 viously descended through epinasty — namely, at the joint where 

 united to the main peduncle. As this upward movement 

 occurred with plants kept in the dark and in whatever position 

 the main peduncle was fastened, it could not have been caxised 

 by heliotropism or apogeotropism, but by hyponasty. Besides 

 this movement at the joint, there is another of a very different 

 kind, for the sub-peduncle becomes upwardly bent in the middle 

 part. If the sub-peduncle happens at the time to be inclined 

 much downwards, the upward curvature is so great that the 

 whole forms a hook. The upper end bearing the capsule, thus 

 always places itself upright, and as this occurs in darkness, and 

 in whatever position the main peduncle may have been secured. 



