CHAP. XI. TKANSMITTED EFFECTS : VICIA. 529 



distorted ; so that this amount of oblique amputation was not. 

 sufficient. Out of the above 30 radicles, only one or two showed 

 in the first 24 h. any distortion, but this became plain in the 

 19 cases on the second day, and still more conspicuous at the 

 close of the third day, by which time new tips had been partially 

 or completely regenerated. When therefore a new tip is re- 

 formed on an oblique stump, it probably is developed sooner on 

 one side than on the other : and this in some manner excites 

 the adjoining part to bend to one side. Hence it seems probable 

 that Sachs unintentionally amputated the radicles on which he 

 experimented, not strictly in a transverse direction. 



This explanation of the occasional irregular growth of radicles 

 with amputated tips, is supported by the results of cauterising 

 their tips; for often a greater length on one side than on the 

 other was unavoidably injured or killed. It should be re- 

 marked that in the following trials the tips were first dried 

 with blotting-paper, and then slightly rubbed with a dry stick 

 of nitrate of silver or lunar caustic. A few touches with the 

 caustic suffice to kill the root-cap and some of the upper layers 

 of cells of the vegetative point. Twenty-seven radicles, some 

 young and very short, others of moderate length, were suspended 

 vertically over water, after being thus cauterised. Of these some 

 entered the water immediately, and others on the second day. 

 The same number of uncauterised radicles of the same age 

 were observed as controls. After an interval of three or four 

 days the contrast in appearance between the cauterised and 

 control specimens was wonderfully great. The controls had 

 grown straight downwards, with the exception of the normal 

 curvature, which we have called Sachs' curvature. Of the 

 27 cauterized radicles, 15 had become extremely distorted; 6 of 

 them grew upwards and formed hoops, so that their tips some- 

 times came into contact with the bean above ; 5 grew out 

 rectangularly to one side ; only a few of the remaining 12 were 

 quite straight, and some of these towards the close of our 

 observations became hooked at their extreme lower ends. 

 Radicles, extended horizontally instead of vertically, with their 

 tips cauterised, also sometimes grew distorted, but not so com- 

 monly, as far as we could judge, as those suspended vertically; 

 for this occurred with only 5 out of 19 radicles thus treated. 



Instead of cutting off the tips, as in the first set of experi- 

 ments, we next tried the effects of touching horizontally ex- 

 tended radicles with caustic in the manner just described. But 



