CHAP. XL TKANSMITTED EFFECTS : VICIA. 525 



accident the* root-cap alone and not the vegetative point was 

 found to have been amputated ; so that this case formed no real 

 exception arid might have been excluded. 



Five radicles were extended horizontally like the last, and 

 had their tips cut off for a length of 1 mm. ; after 22-23 h., four 

 of them were still horizontal, and one was slightly geotropic ; 

 after 48 h. the latter had become vertical ; a second was also 

 somewhat geotropic ; two remained approximately horizontal ; 

 and the last or fifth had grown in a disordered manner, for it 

 was inclined upwards at an angle of 65 above the horizon. 



Fourteen radicles were extended horizon tally at a little height 

 over the water with their tips cut off for a length of T5 mm. ; 

 after 12 h. all were horizontal, whilst five control or standard 

 specimens in the same jar were all bent greatly downwards. 

 After 24 h. several of the amputated radicles remained hori- 

 zontal, but some showed a trace of geotropism, and one was 

 plainly geotropic, for it was inclined at 40 beneath the horizon. 



Seven horizontally extended radicles from which the tips had 

 been cut off for the unusual length of 2 mm. unfortunately were 

 not looked at until 35 h. had elapsed ; three w^ere still horizontal, 

 but, to our surprise, four were more or less plainly geotropic. 



The radicles in the foregoing cases were measured before their 

 tips were amputated, and in the course of 24 h. they had all 

 increased greatly in length; but the measurements are not 

 worth giving. It is of more importance that Sachs found that 

 the rate of growth of the different parts of radicles with 

 amputated tips was the same as with unmutilated ones. Alto - 

 gether twenty-nine radicles were operated on in the manner 

 above described, and of these only a few showed any geotropic 

 curvature within 24 h. ; whereas radicles with unmutilated tips 

 always became, as already stated, much bent down in less than 

 half of this time. The part of the radicle which bends most lies 

 at the distance of from 3 to 6 mm. from the tip, and as the 

 bending part continues to grow after the operation, there does 

 not seem any reason why it should not have been acted on by 

 geotropism, unless its curvature depended on some influence 

 transmitted from the tip. And we have clear evidence of such 

 transmission in Ciesielski's experiments, which we repeated and 

 extended in the following manner. 



Beans were embedded in friable peat with the hilum down- 

 wards, and after their radicles had grown perpendicularly down 

 for a length of from ^ to 1 inch, sixteen were selected which 



