CHAP. IY. 



DICOTYLEDONS. 



229 



Fig. 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 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 Crambe maritima : circumnutation of leaf, 



disturbed by being insufficiently illumi- 

 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.) Brassica oleracea (Cruciferse). Hofmeister 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 



preceding night ; and this 

 may be attributed to the 

 leaf adjusting itself to the 

 dim light, coming exclu- 

 sively from above. 



Flora,' 1873, p. 437 



