270 



MODIFIED CIRCUMNUTATION. 



Chap. V. 



yoiuig leaf was traced during ij days, and the tracing here given 

 (Fig. 121) shows that it descended at first in a nearly straight 



line, but afterwards zigzagged, 



Fig. 121. 



Pin^iu' t^rster : epinastic downward 

 movenient of a young leaf, pro- 

 duced by a young plant in a pot, 

 traced on a vei'tical glass under a 

 skylight, from 6.4.5 a.m. June 2nd 

 to 10.40 P.M. 6th. 



making one or two little loops. 

 The diverging and descend- 

 ing movements of a rather 

 older leaf were also traced 

 (see former Fig. 113, p. 251) : 

 it descended during the first 

 day and night ia a sonie- 

 what zigzag line ; it then cir- 

 cumnutated round a small 

 space and again descended. 

 By this time the leaf had 

 nearly assumed its final posi- 

 tion, and now plainly circum- 

 nutated. As in the case of the 

 Carnation, the leaves, whilst 

 very young, do not seem to he 

 much affected by geotropism 

 or heliotropism, for those on a 

 young plant laid horizontally, 

 and those on another plant 

 left upright, both kept in the 

 dark, continued to diverge in 

 the usual manner without 

 bending to either side. 



With Cohcea scandens, the 

 young leaves, as they succes- 

 sively diverge from the lead- 

 ing shoot which is bent to 

 one side, rise up so as to pro- 

 ject vertically, and th«y retain 

 this position for some time 

 whilst the tendril is revolving. 

 The diverging and ascending 

 movements of the petiole of 

 one such a leaf, were traced on 

 a vertical glass under a sky- 

 light ; and the course pursued 

 was in most parts nearly 

 straight, but there were twc 



