244 



CmCUMNUTATION OF LEAVES. CHAP. IV. 



of raw meat was placed on the leaf, which caused the lobes to 

 close together very slowly in the course of two days ; and the 

 oscillations continued during this whole time and for the next 

 two days. After nine additional days the leaf began to open 

 and the margins were a little everted, and now the apex of the 

 glass filament remained for long periods motionless, and then 

 moved backwards and forwards for a distance of about y^o of 

 an inch slowly, without any jerks. Nevertheless, after warming 

 the leaf with a taper held close to it, the jerking movement 

 recommenced. 



This same leaf had been observed 2 months previously, and 

 was then found to be oscillating or jerking. We may therefore 

 infer that this kind of movement goes on night and day for a 

 very long period ; and it is common to young unexpanded leaves 

 and to leaves so old as to have lost their sensitiveness to a 

 touch, but which were still capable of absorbing nitrogenous 

 matter. The phenomenon when well displayed, as in the young 

 leaf just described, is a very interesting one. It often brought 

 before our minds the idea of effort, or of a small animal 

 struggling to escape from some constraint. 



(16.) Eucalyptus resinifera (Myrtacese, Fam. 94). A young leaf, 

 two inches in length together with 

 the, petiole, produced by a lateral 

 shoot from a cut-down tree, was 

 observed in the usual manner. 

 The blade had not as yet as- 

 sumed its vertical position. On 

 June 7th only a few observations 

 were made, and the tracing merely 

 showed that the leaf had moved 

 three times upwards and three 

 downwards. On the following 

 day it was observed more fre- 

 quently; and two tracings were 

 made (see A and B, Fig. 108), as 

 a single one would have been too 

 complicated. The apex changed 

 its course 13 times in the course 

 of 16 h., chiefly up and down, but 

 The actual amount of movement 



Fig. 108. 



Eucalyptus resinifera : circum nu- 

 tation of a leaf, traced, A, from 

 6.40 A.M. to 1 P.M. June 8th ; 

 B, from 1 P.M. 8th to 8.30 A.M. 

 9th. Apex of leaf 14 inches 

 from the horizontal glass, so 

 figures considerably magnified. 



with some lateral movement, 

 in any one direction was small. 

 (17.) Dahlia (garden var.) (Composite, Fam. 122). A fine young 



