CLIMBING PLANTS. 409 
of a grain. They will clasp thin withered blades of grass, 
the soft young leaves of a maple, or the lateral flower pe- 
duncles of the quaking grass Briza; the latter are only 
about as thick as a hair from a man's beard, but they were 
completely surrounded and clasped. 
The first petiole of Tropceolum tricolorum var. grandi- 
lorum bear no lamine or blades, and are very sensitive to 
touch, sometimes bending into a complete ring in six min- 
utes. The next filaments above have their tips slightly 
enlarged, and those still farther up the stem still more 
enlarged ; so we find all grades, from tendrils to leaves with 
large blades. All of these petioles are sensitive; those 
without blades acting in every way like genuine tendrils; 
the latter are short lived, however, dropping off as soon as 
the petioles of the true leaves have clasped the support 
above. The most remarkable fact, and which I have ob- 
served in no other species of the genus, is that the filaments 
and petioles of the young leaves, if they catch no object, 
after standing in their original position for some days, spon- 
taneously and slowly move, oscillating a little from side to 
side towards the stem of the plant. Hence all the petioles 
and filaments, though arising on different sides of the axis, 
ultimately bend towards and clasp either their own stem or 
the supporting stick. The petioles and filaments often be- 
come, after a time, in some degree contracted, presenting 
features much like true tendrils. 
Maurandia semperflorens (SScrophulariacem) has flower 
peduncles which are sensitive like tendrils, and exhibit re- 
volving powers. These spontaneous movements seem to be 
of no service to the plant as they lose the power when the 
flower is old enough to open. The leaf-stalks and internodes 
of this plant do not twine. 
hospermum scandens var. purpureum when young has 
sensitive internodes. When a petiole clasps a stick it 
draws the base of the internode against it; and then the 
internode itself bends towards the stick, which is thus 
AMER. NATURALIST, VOL. IV. 52 
