If a tendril catches nothing, after a considerable
interval of time the tips of the branches curl a little inwards; but
if it clasps some object, the whole contracts spirally.
SMILACEAE.--Smilax aspera, var. maculata.--Aug. St.-Hilaire {28}
considers that the tendrils, which rise in pairs from the petiole,
are modified lateral leaflets; but Mohl (p. 41) ranks them as
modified stipules. These tendrils are from 1.5 to 1.75 inches in
length, are thin, and have slightly curved, pointed extremities.
They diverge a little from each other, and stand at first nearly
upright. When lightly rubbed on either side, they slowly bend to
that side, and subsequently become straight again. The back or
convex side when placed in contact with a stick became just
perceptibly curved in 1 hr. 20 m., but did not completely surround it
until 48 hrs. had elapsed; the concave side of another became
considerably curved in 2 hrs. and clasped a stick in 5 hrs. As the
pairs of tendrils grow old, one tendril diverges more and more from
the other, and both slowly bend backwards and downwards, so that
after a time they project on the opposite side of the stem to that
from which they arise.
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