176 Cuap. IV. 
TENDRIL-BEARERS, 
the part which is wound round a support which 
chiefly becomes thicker and stronger; I have seen, 
for instance, this part of a tendril of Bignonia xqui- 
noctialis twice as thick and rigid as the free basal part. 
Tendrils which have caught nothing soon shrink and 
wither; but in some species of Bignonia they disarti- 
culate and fall off like leaves in autumn. 
Any one who had not closely observed tendrils of 
many kinds would probably infer that their action was 
uniform. This is the case with the simpler kinds, 
which simply curl round an object of moderate thick- 
ness, whatever its nature may be.* But the genus 
Bignonia shows us what diversity of action there may 
be between the tendrils of closely allied species. In 
all the nine species observed by me, the young in- 
ternodes revolve vigorously; the tendrils also re- 
volve, but in some of the species in a very feeble 
manner ; and lastly the petioles of nearly all revolve, 
though with unequal power. The petioles of three of the 
species, and the tendrils of all are sensitive to contact. 
In the first-described species, the tendrils res mble 
in shape a bird’s foot, and they are of no service to the 
stem in spirally ascending a thin upright stick, but 
they ean seize firm hold of a twig or branch. When 
* Sachs, however (‘ Text-Book 
of Botany,’ Eng. Translation, 1875, 
adapted to clasp supports of 
different thicknesses. He further 
p. 280), has shown that which — 
I overlooked, namely, that the 
tendrils of different species are 
shows that after a tendril has 
clasped a support it subsequently 
tightens its hold. 
