CHAP. VIII. APHELIOTROPISM. 433 



contact with the trunks of trees.* The stem of a young plant 

 was tied to a stick at the base of a pair of fine tendrils, which 

 projected almost vertically upwards; and it was placed in 

 front of a north-east window, being protected on all other sides 

 from the light. The first dot was made at 6.45 A.M., and by 

 7.35 A.M. both tendrils felt the full influence of the light, for 

 they moved straight away from it until 9.20 A.M., when they 

 circumnutated for a time, still moving, but only a little, from 

 the light (see^Fig. 178 of the left-hand tendril). After 3 P.M. 

 they again moved rapidly away from the light in zigzag lines. 

 By a late hour in the evening both had moved so far, that 

 they pointed in a direct line from the light. During the night 

 they returned a little in a nearly opposite direction. On the 

 following morning they again moved from the light and con- 

 verged, so that by the evening they had become interlocked, 

 still pointing from the light. The right-hand tendril, whilst 

 converging, zigzagged much more than the one figured. Both 

 tracings showed that the apheliotropic movement was a modi- 

 fied form of circumnutation. 



Cyclamen Persicum. Whilst this plantis in flower the peduncles 

 stand upright, but their uppermost part is hooked so that the' 

 flower itself hangs downwards. As soon as the pods begin to 

 swell, the peduncles increase much in length and slowly curve 

 downwards, but the short, upper, hooked part straightens itself. 

 Ultimately the pods reach the ground, and if this is covered 

 with moss or dead leaves, they bury themselves. We have often 

 seen saucer-like depressions formed by the pods in damp sand 

 or sawdust ; and one pod ( 3 of inch in diameter) buried itself 

 in sawdust for three-quarters of its length. f We shall have 

 occasion hereafter to consider the object gained by this burying 

 process. The peduncles can change the direction of their cur- 

 vature, for if a pot, with plants having their peduncles already 

 bowed downwards, be placed horizontally, tjiey slowly bend 

 at right angles to their former direction towards the centre of 

 the earth. We therefore at first attributed the movement to 

 geotropism ; but a pot which had lain horizontally with the pods 



* 'The Movements and Habits tanic Garden,' Canto., iii. p. 126), 



of Climbing Plants,' 1875, p. 97. the pods forcibly penetrate the 



* f The peduncles of several earth. See also Grenier and 



other species of Cyclamen twist Godron, 'Florede France,' torn. ii. 



themselves into a spire, and ac- p. 459. 

 cording to Erasmus Darwin (' Bo- 



