Chap. I. YICIA. 31 



We next experimented on nearly a score of radicles by allowing 

 them to grow downwards over inclined plates of smoked glass, 

 in exactly the same manner as with .Slsculus and Phaseolus. 

 Some of the plates were inclined only a few degrees beneath 

 the horizon, but most of them between 60° and 75°. In the 

 latter cases the radicles in growing downwards were deflected 

 only a little from the direction which they had followed whilst 

 germinating in sawdust, and they pressed lightly on the glass- 

 plates (Fig. 21). Five of the most distinct tracks are here 

 copied, and they are aU slightly sinuous, showing circumnutii- 

 tion. Moreover, a close examination of almost every one of the 

 tracks clearly showed that the tips in their downward course 

 had alternately pressed with greater or less force on the plates, 

 and had sometimes risen up so as nearly to leave them for short 

 intervals. The distance between the extreme right and left 

 positions of the radicle A was 0'7 mm., ascertained in the same 

 manner as in the case of Phaseolus. 



Epicotyl. — At the point where the radicle had protruded from 

 a bean laid on its side, a flattened solid lump projected "1 of an 

 inch, in the same horizontal plane with the bean. This protuber- 

 ance consisted of the convex summit of the arched epicotyl; 

 and as it became developed the two legs of the arch curved 

 themselves laterally upwards, owing to apogeotropism, at such 

 a rate that the arch stood highly inclined after 14 h., and 

 vertically in 48 h. A filament was fixed to the crown of 

 the protuberance before any arch was visible, but the basal 

 half grew so quickly that on the second morning the end of the 

 filament was bowed greatly downwards. It was therefore re- 

 moved and fixed lower down. The line traced during these two 

 days extended in the same general direction, and was in parts 

 nearly straight, and in others plainly zigzag, thus giving some 

 evidence of circumnutation. 



As the arched epicotyl, in whatever position it may be placed, 

 bends quickly upwards through apogeotropism, and as the two 

 legs tend at a very early age to separate from one another, as 

 soon as they are relieved from the pressure of the surrounding 

 earth, it was diflcult to ascertain positively whether the epicotyl, 

 whilst remaining arched, circumnutated. Therefore some rather 

 deeply buried beans were uncovered, and the two legs of the 

 arches were tied together, as had been done with the epicotyl 

 of TropsBolum and the hypocotyl of the Cabbage. The move- 

 ments of the tied arches were traced in the usual manner on 



