CHAP. IV. 



DICOTYLEDONS. 



229 



rig. 95. 



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 circumnutating ; 

 but the proper periodicity 

 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 rnid-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 Crambe maritima: circumnutation of leaf, 

 preceding night; and this disturbed by being insufficiently illumi- 

 , i ot+^K,,*^ * *!, nated from above, traced from 7.50 A.M. 

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

 15J inches from the vertical glass, so that 

 the tracing was much magnified, but is 

 here reduced to one-fourth of original scale. 



(4.) Bratsica ohracta (Crucifene). Hofmeister and Batalin * 

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

 d;iy. We covered a young plant, bearing 8 leaves, under a large 

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



7: Sift 



may be attributed to the 

 leaf adjusting itself to the 

 dim light, coming exclu- 

 sively from above. 



Flora,' 1873, p. 437 



