Chap. IV. 



DICOTYLEDONS. 



229 



was deflected, so that the filament projected almost horizontally, 

 and its movements were traced during 48 h. on a vertical glass, 

 as shown in the accompanying figure (Fig. 95). We here plainly 

 see that the leaf was con- 

 tinually circunmutating ; _ ^u 



but the proper periodicity 6«je<t.m.2S«'v 

 of its movements was dis- \ \ 



turbed by its being only 

 dimly illuminated from 

 above through a double 

 skylight. We infer that 

 this was the case, because 

 two leaves on plants grow- 

 ing out of doors, had their 

 angles above the horizon 

 measured in the middle 

 of the day and at 9 to 

 about 10 P.M. on succes- 

 sive nights, and they 

 were found at this latter 

 hour to have risen by an 

 average angle of 9° above 

 their mid-day position: 

 on the following morning 

 they fell to their former 

 position. Now it may be 

 observed in the diagram 

 that the leaf rose during 

 the second night, so that 

 it stood at 6.40 a.m. higher 

 than at 10.20 p.m. on the 

 preceding night ; and this 

 may be attributed to the 

 leaf adjusting itself to the 

 dim light, coming exclu- 

 sively from above. 



(4.) Brassica oleracfa (Cruciferse). — Hoftneister and Batalin " 

 state that the leaves of the cabbage rise at night, and fall by 

 day. We covered a young plant, bearing 8 leaves, under a large 

 bell-glass, placing it in the same position with respect to the 



-•.S0'a.m.S3<^ 



g:sitam,.8dm 



Crimhe maritima: circumnutation of leaf, 

 disturbed by being insuffioiently illumi- 

 nated from above, traced from 7.50 A.M. 

 June 23rd to 8 A.M. 25th. Apex of leaf 

 151 inches from the vertical glass, so that 

 the tracing was much magnified, but is 

 here reduced to one-fourth of original scale. 



» ' Flora," 1873, p. 437 



