Cuar. IV, SUMMARY. 173 
by a touch of equal force on opposite sides, did not 
bend. The inferior and lateral surfaces of the tendrils 
of Mutisia are sensitive, but not the upper surface. 
With branched tendrils, the several branches act 
alike; but in the Hanburya the lateral spur-like 
branch does not acquire (for excellent reasons which 
have been explained) its sensitiveness nearly so 
soon as the main branch. With most tendrils the 
lower or basal part is either not at all sensitive, or 
sensitive only to prolonged contact. We thus see 
that the sensitiveness of tendrils is a special and 
localized capacity. It is quite independent of the 
power of spontaneously revolving; for the curling of 
the terminal portion from a touch does not in the least 
interrupt the former movement. In Bignonia unguis 
and its close allies, the petioles of the leaves, as well 
as the tendrils, are sensitive to a touch. 
Twining plants when they come into contact with a 
stick, curl round it invariably in the direction of their 
revolving movement; but tendrils curl indifferently 
to either side, in accordance with the position of the 
stick and the side which is first touched. The clasping 
movement of the extremity is apparently not steady, 
but undulatory or vermicular in its nature, as may be 
inferred from the curious manner in which the tendrils 
of the Echinocystis slowly crawled round a smooth 
stick, 
As with a few exceptions tendrils spontaneously 
revolve, it may be asked,—why have they been endowed 
with sensitiveness ?—why, when they come into contact 
