Ghap. XI. TBANSMITTED EFFECTS : VICIA. 



52? 



Fig. 195. 



former trial ; and after their tips (1-& mm. in length) hail been 

 amputated, they were placed vertically in damp peat. Of these, 

 three were not in the least affected and continued for days to 

 grow straight downwards. Pour showed after 8 h. 30 m. a mere 

 trace of curvature in the direction in which they had been acted 

 on by geotropism ; and in this respect they differed much from 

 those which had been exposed for 

 1 h. 37 m., for many of the latter 

 were plainly curved in 6 h. The 

 curvature of one of these four 

 radicles almost disappeared after 

 24 h. In the s.econd, the cur- 

 vature increased during two days 

 and then decreased. The third 

 radicle became permanently bent, 

 so that its terminal part made an 

 angle of about 45° with its original 

 vertical direction. The fourth 

 radicle became horizontal. These 

 two latter radicles oontintied 

 during two more days to grow 

 in the peat in the same directions, 

 that is, at an angle of 45° be- 

 neath the horizon and horizon- 

 tally. By the fourth morning new 

 tips had been re-formed, and now 

 geotropism was able to act on 

 them again, and they became 

 bent perpendicularly downwards, 

 exactly as in the case of the 

 five radicles described in the 

 last paragraph and as is shown in 

 the figure (Fig. 195) here given. 



Lastly, five other radicles were similarly treated, but were ex- 

 posed to geotropism during only 45 m. After 8 h. 80 m. only 

 one was doubtfully affected; after 24 h. two were just per- 

 ceptibly curved towards the side which had been acted on by 

 geotropism ; after 48 h. the one first mentioned had a radius of 

 curvature of 60 mm. That this curvature was due to the action 

 of geotropism during the horizontal position of the radicle, waa 

 shown after 4 days, when a new tip had bten reformed, for it 

 then grew perpendicularly downwards. We learn from thie 



Vicia faba : radicle, rectangularly 

 bent at A, after the amputation 

 of the tip, due to the previous 

 influence of geotropism. L, side 

 of bean which lay on the peat, 

 whilst geotropism acted on the 

 radicle. A, point of chief cur- 

 vature of the radicle, whilst 

 standing vertically downwards. 

 B, point of chief curvature after 

 theregenerationof the tip, when 

 geotropism again acted. C, re- 

 generated tip. 



