CHAP. IIL OF THE KADICLE OF THE BEAN. 141 



of common card were affixed with thick gum- water to 

 the tips of the radicles of seven beans, as a pre- 

 liminary trial. Six of these were plainly acted on, 

 and in two cases the radicles became coiled up into 

 complete loops. One radicle was curved into a semi- 

 circle in so short a period as 6 h. 10 m. The 

 seventh radicle which was not affected was apparently 

 sickly, as it became brown on the following day ; so 

 that it formed no real exception. Some of these trials 

 were made in the early spring during cold weather in 

 a sitting-room, and others in a greenhouse, but the 

 temperature was not recorded. These six striking 

 cases almost convinced us that the apex was sensitive, 

 but of course we determined to make many more trials. 

 As we had noticed that the radicles grew much more 

 quickly when subjected to considerable heat, and as 

 we imagined that heat would increase their sensitive- 

 ness, vessels with germinating beans suspended in 

 damp air were placed on a chimney-piece, where they 

 were subjected during the greater part of the day to a 

 temperature of between 69 and 72 F. ; some, how- 

 ever, were placed in the hot-house where the tempera- 

 ture was rather higher. Above two dozen beans were 

 thus tried; and when a square of glass or card did 

 not act, it was removed, and a fresh one affixed, this 

 being often done thrice to the same radicle. There- 

 fore between five and six dozen trials were altogether 

 made. But there was moderately distinct deflection 

 from the perpendicular and from the attached object 

 in only one radicle out of this large number of cases. 

 In five other cases there was very slight and doubtful 

 deflection. We were astonished at this result, and 

 concluded that we had made some inexplicable mis- 

 take in the first six experiments. But before finally 

 relinquishing the subject, we resolved to make one 



