CHAP. L QUERCUS AND COEYLUS. 55 



alternately with unequal force on the glass ; so that it had 

 moved a little in two planes at right angles to one another. In 

 the eighth and last case (C) it had moved very little laterally, 

 but had alternately left the glass and come into contact with it 

 again. There can be no doubt that in the last four cases the 

 radicle of the oak circumnutated whilst growing downwards. 



Fig. 41. 



Q'tercus rrf>ur: tracks left on inclined smoked glass-plates by tips of 

 radicles in growing downwards. Plates A and C inclined at Gi> and 

 plate B at 68 to the horizon. 



Corylus avellana (Corylaceae). The epicotyl breaks through 

 the ground in an arched form ; but in the specimen which was 

 first examined, the apex had become decayed, and the epicotyl 

 grew to some distance through the soil, in a tortuous, almost 

 1 orizpntal direction, like a root. In consequence of this injury 

 it had emitted near the hypogean cotyledons two secondary 

 shoots, and it was remarkable that both of these were arched, 

 like the normal epicotyl in ordinary cases. The soil was removed 

 from around one of these arched secondary shoots, and a glass 

 filament was affixed to the basal leg. The whole was kept 

 damp beneath a metal-box with a glass lid, and was thus illumi- 

 nated only from above. Owing apparently to the lateral pressure 

 of the earth being removed, the terminal and bowed-down part 

 of the shoot began at once to move upwards, so that after 

 '24 h. it formed a right angle with the lower part. This lower 

 part, to which the filament was attached, also straightened 

 itself, and moved a little backwards from the upper part. Con- 

 sequently a long line was traced on the horizontal glass; and 

 5 



