Chap. I. TWINING PLANTS. 37 



when placed in a room with the light entering on one 

 side, twine round sticks between 3 and 4 inches in 

 diameter ; for this interfered, in a manner presently 

 to be explained, with the revolving movement. In the 

 open air, however, the Phaseolus twined round a 

 support of the above thickness, but failed in twining 

 round one 9 inches in diameter. JN^evertheless, some 

 twiners of the warmer temperate regions can manage 

 this latter degree of thickness ; for I hear from 

 Dr. Hooker that at Kew the Smscus androgynus has 

 ascended a column 9 inches in diameter ; and although 

 a Wistaria grown by me in a small pot tried in vain 

 for weeks to get round a post between 5 and 6 inches 

 in thickness, yet at Kew a plant ascended a trunk 

 above 6 inches in diameter. The tropical twiners, on 

 the other hand, can ascend thicker trees ; I hear from 

 Drs. Thomson and Hooker that this is the case with 

 the Butea parvijlora, one of the Menispermaceae, and 

 with some Dalbergias and other Leguminosse.* This 

 power would be necessary for any species which had 

 to ascend by twining the large trees of a tropical forest ; 

 otherwise they would hardly ever be able to reach the 

 light. In our temperate countries it would be injurious 

 to the twining plants which die down every year if 



* Fritz Miiller states (ibid. p. ispermaceae. He adds in his 

 349) that he saw on one occasion in letter to me tbat most of the 

 the forests of South Brazil a trunk climbing plants which there 

 about five feet in circumference ascend thick trees, are root- 

 spirally ascended by a plant, climbers ; some being tendril- 

 appareutly belonging to the Men- bearers. 



