Cuap. IV. CUCURBITACE. 131 
a grain in weight caused a temporary flexure. The 
lower part was repeatedly rubbed rather roughly, but 
no curvature ensued; yet this part is sensitive to pro- 
longed pressure, for when it came into contact with a 
stick, it would slowly wind round it. 
One of my plants bore two shoots near together, 
and the tendrils were repeatedly drawn across one 
another, but it is a singular fact that they did not 
once catch each other. It would appear as if they had 
become habituated to contact of this kind, for the 
pressure thus caused must have been much greater 
than that caused by a loop of soft thread weighing 
only the one-sixteenth of a grain. J have, however, 
seen several tendrils of Bryonia dioica interlocked, but 
they subsequently released one another. The tendrils 
of the Echinocystis are also habituated to drops of 
water or to rain; for artificial rain made by violently 
flirting a wet brush over them produced not the least 
effect. 
The revolving movement of a tendril is not stopped 
by the curving of its extremity after it has been 
touched. When one of the lateral branches has firmly 
clasped an object, the middle branch continues to 
revolve. When a stem is bent down and secured, so 
that the tendril depends but is left free to move, its pre- 
vious revolving movement is nearly or quite stopped ; 
but it soon begins to bend upwards, and as soon as it 
has become horizontal the revolving movement recom- 
mences. I tried this four times; the tendril generally 
rose to a horizontal position in an hour or an hour and 
