Cap. 1. 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. Nevertheless, some 
twiners of the warmer temperate regions can manage 
this latter degree of thickness; for I hear from 
Dr. Hooker that at Kew the Ruscus 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 parviflora, one of the Menispermacee, and 
with some Dalbergias and other Leguminose.* 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 
in his 
* Fritz Miller states (ibid. p.. 
349) that he saw on one occasion in 
the forests of South Brazila trunk 
about five feet in circumference 
spirally ascended by a plant, 
apparently belonging to the Men- 
ispermacese. He adds 
letter to me that most of the 
climbing plants which there 
ascend thick trees, are root- 
climbers; some being tendril- 
bearers. 
