32 CIECUMNUTATION OF SEEDLINGS. Chap. L 



two occasions during three days. But the tracings made under 

 such unnatural conditions are not worth giving ; and it need 

 only be said that the lines were decidedly zigzag, and that 

 small loops were occasionally formed. We may therefore con- 

 clude that the epicotyl circumnutates whilst, still arched and 

 before it has grown talL enough to break through the surface 

 of the ground. 



In order to observe the movements of the epicotyl at a some- 

 what more advanced age, a filament was fixed near the base of 

 one which was no longer arched, for its upper half now formed 

 a right angle with the lower half. This bean had germinated 

 on bare damp sand, and the epicotyl began to straighten itself 

 much sooner than would have occurred if it had been properly 

 planted. The course pursued during 50 h. (from 9 a.m. Dec. 

 26th, to 11 A.M. 28th) is here shown (Fig. 22) ; and we see 



Fig. 22. 



Vicia fdba: circumnutation of young epicotyl, traced in darkness during 

 50 hours on a horizontal glass. Movement of bead of filament mag- 

 nified 20 times, here reduced to one-half of original scale. 



that the epicotyl circumnutated during the whole time. Its 

 basal part grew so much during the 50 h. that the filament 

 at the end of our observations was attached at the height of 

 '4 inch above the upper surface of the bean, instead of close 

 to it. If the bean had been properly planted, this part of the 

 epicotyl would still have been beneath the soil. 



Late in the evening of the 28th, some hours after the above 

 observations were completed, ■ the epicotyl had grown much 

 straighter, for the upper part now formed a widely open angle 

 with the lower part. A filament was fixed to the upright basal 

 part, higher up than before, close beneath the lowest scale-lika 

 process or homologue of a leaf; and its movement was traced 



