228 



CIRCUMNUTATION OF LEAVES. 



Chap. IV. 



across its apex ; it was observed for 43 h., and during the whole 

 of this time it circumnutated in a nearly similar manner, but 

 to a very small extent. The tracing given (Kg. 93) relates 

 only to the movements during the first 26 h. 



(2.) (-jlauHum luteum (Papave- 

 racese, Fam. 12). — A young plant, 

 bearing only 8 leaves, had a fila- 

 ment attached to the youngest leaf 

 but one, which was 3 inches in 

 length, including the petiole. The 

 circumnutating movement was 

 traced during 47 h. On both days 

 the leaf descended from before 7 a.m. 

 until about 11 a.m., and then 

 ascended slightly during the rest 

 of the day and the early part of 

 the night. During the latter part 

 of the night it fell greatly. It did 

 not ascend so much during the 

 second as during the first day, and 

 it descended considerably lower on 

 the second night than on the first. 

 This difference was probably due 

 to the illumination from above 

 having been insufficient during the 

 two days of observation. Its course 

 during the two days is shown in 

 Fig. 94. 



(3.) Cramhe maritima (Cruciferse, 

 Tarn. 14). — A leaf 9^ inches in length 

 on a plant not growing vigorously 

 was first observed. Its apex was 

 in constant movement, but this 

 could hardly be traced, from being 

 so small in extent. The apex, how- 

 ever, certainly changed its course at 

 least 6 times in the course of 14 h. 

 A more vigorous young plant, bear- 

 ing only 4 leaves, was then selected, 

 and a filament was affixed to the 

 midrib of the third leaf from the base, which, with the petiole, was 

 5 inches in length. The leaf stood up almost vertically, but the tip 



(JlituriUM luteum : circumnnta- 

 tion of young leaf, traced 

 from 9.30 a.m. June 14th 

 to 8.30 A.M. 16th. Tracing 

 not much magnified, as apex 

 of leaf stood- only 5^ inches 

 from the glass. 



