166 SENSITIVENESS OF THE AI'EX Chap. HI 



of experiments, when the tips of several were greatly 

 blackened and injured on one side, so that their growth 

 was arrested, a length of less than 3 mm. became 

 curved towards the much blackened side, owing to the 

 continued growth of the opposite side. This differ- 

 ence in the results is interesting, for it shows that too 

 strong an irritant does not induce any transmitted 

 effect, and does not cause the adjoining, upper and 

 growing part of the radicle to bend. We have analo- 

 gous cases with Drosera, for a strong solution of car- 

 bonate of ammonia when absorbed by the glands, or 

 too great heat suddenly applied to them, or crushing 

 them, does not cause the basal part of the tentacles 

 to bend, whilst a weak solution of the carbonate, or a 

 moderate heat, or slight pressure always induces such 

 bending. Similar results were observed with Dionsaa 

 and Pinguicula. 



The effect of cutting off with a razor a thin slice 

 from one side of the conical apex of 14 young and 

 short radicles was next tried. Six of them after beiug 

 operated on were suspended in damp air ; the tips of 

 the other eight, similarly suspended, were allowed to 

 enter water at a temperature of about 65° F. It was 

 recorded in each case which side of the apex had 

 been sliced off, and when they were afterwards 

 examined the direction of the curvature was noted, 

 before the record was consulted. Of the six radicles 

 in damp air, three had their tij)s curved after an 

 interval of 10 h. 15 m. directly away from the sliced 

 surface, whilst the other three were not affected and 

 remained straight; nevertheless, one of them after 

 13 additional hours became slightly curved from the 

 sliced surface. Of the eight radicles with their tips 

 immersed in water, seven were plainly curved away 

 from the sliced surfaces after 10 h. 15 m. : and witt 



