If the tendril catches nothing, it first slowly bends
downwards, and then its power of clasping is lost. Very soon
afterwards it disarticulates itself from the petiole, and drops off
like a leaf in autumn. I have seen this process of disarticulation
in no other tendrils, for these, when they fail to catch an object,
merely wither away.
Bignonia venusta.--The tendrils differ considerably from those of the
previous species. The lower part, or tarsus, is four times as long
as the three toes; these are of equal length and diverge equally, but
do not lie in the same plane; their tips are bluntly hooked, and the
whole tendril makes an excellent grapnel. The tarsus is sensitive on
all sides; but the three toes are sensitive only on their outer
surfaces. The sensitiveness is not much developed; for a slight
rubbing with a twig did not cause the tarsus or the toes to become
curved until an hour had elapsed, and then only in a slight degree.
Subsequently they straightened themselves. Both the tarsus and toes
can seize well hold of sticks. If the stem is secured, the tendrils
are seen spontaneously to sweep large ellipses; the two opposite
tendrils moving independently of one another.
Pages:
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126