CLIMBING PLANTS. 411 
for climbing. They are formed by the modification of leaves 
with their petioles, of flower-peduncles, perhaps also of 
branches and stipules. The species of tendril bearers de- 
scribed belong to ten natural families. Species of Bignonia 
and some others taken together, afford connecting links 
between twiners, leaf-climbers, tendril-bearers, and root 
climbers. Some little time after the stem of Bignonia 
Tweedyana has twined round an upright. stick, and is se- 
curely fastened to it by the clasping petioles and tendrils, it 
emits at the base of its leaves aérial roots which curve partly 
round and adhere to the stick; so that this one species of 
Bignonia combines four different methods of climbing, gen- 
erally characteristic of distinct plants, namely, twining, leaf- 
climbing, tendril-climbing, and root-climbing. 
The movements of Bignonia venusta are quite compli- 
cated. Not only the tendrils but the petioles bearing them 
revolve; these petioles, however, are not in the least sensi- 
tive. Thus the young internodes, the petioles, and the 
tendrils, all at the same time, go on revolving together, but 
at different rates. Moreover the movements of the opposite 
petioles and tendrils are quite independent of each other. . 
One other curious point remains to be mentioned. Ina few 
days after the toes have closely clasped a stick, their blunt 
extremities become, though not. invariably, developed into 
irregular disk-like balls, which have the singular power of 
adhering firmly to the wood. 
The simple undivided tendril of Bignonia speciosa ends in 
an almost straight, sharp, uncolored point. The whole ter- 
minal part exhibits an odd habit, which in an animal would 
be called an instinct ; for it continually searches for any little 
dark hole into which to insert itself. The tendrils slowly 
travel over the surface of the wood, and when the apex came 
to a hole or a fissure it inserted itself, often bending at right 
angles to the basal part. The same tendril would frequently 
withdraw from one hole and insert its point into a second 
one. Mr. Darwin says: "Improbable as this view may be 
