14 CmCUMNUTATION OF SEEDLINGS. Chap. I 



age to cii-cunmutate irregularly. On the first day the greatei 

 movement (from right to left In the figure) was not in the plane 

 of the vertical and arched hypocotyl, but at right angles to it, or in 

 the plane of the two cotyledons, which were still in close contact. 

 The basal leg of the arch at the time when the filament was 

 affixed to it, was already bowed considerably backwards or 

 from the cotyledons; had the filament been affixed before this 

 bowing occurred, the chief movement would have been at right 

 angles to that shown in the figure. A filament was attached to 

 another buried hypocotyl of the same age, and it moved in a 

 similar general manner, but the line traced was not so complex. 

 This hypocotyl became almost straight, and the cotyledons were 

 dragged from beneath the ground on the evening of the second day 



Fig. 4. 



/ 



Brassica oUracea : circumnutiiting movement of buried and arched hypo- 

 cotyl, with the two legs of the arch tied together, traced on horizontal 

 glass during 33J hours. Movement of the bead of filament magnified 

 about 26 times, and here reduced to one-half original scale. 



Before the above observations were made, some arched hypo- 

 cotyls buried at the depth, of a quarter of an inch were un- 

 covered ; and in order to prevent the two legs of the arch 

 from beginning to separate at once, they were tied together with 

 fine silk. This was done partly because we wished to ascertain 

 how long the hypocotyl, in its arched condition, would continue 

 to move, and whether the movement when not masked and 

 disturbed by the straightening process, indicated circumnu- 

 tation. Firstly, a filament was fixed to the basal leg of an 

 arched hypocotyl close above the summit of the radicle. The 

 cotyledons were still partially enclosed within the seed-coats. 

 The movement was traced (Fig. 4) from 9.20 a.m. on Dsa 



