Cuav. IV. PASSIFLORACE. 155 
not agitated by the wind. The movement after a touch 
is very rapid: I took hold of the lower part of several 
tendrils, and then touched their concave tips with a 
thin twig and watched them carefully through a lens; 
the tips evidently began to bend after the following 
intervals—381, 25, 32, 31, 28,39, 31, and 80 seconds ; so 
that the movement was generally perceptible in half a 
minute after a touch; but on one occasion it was 
distinctly visible in 25 seconds. One of the tendrils 
which thus became bent in 31 seconds, had been 
touched two hours previously and had coiled into a 
helix; so that in this interval it had straightened 
itself and had perfectly recovered its irritability. 
To ascertain how often the same tendril would 
become curved when touched, I kept a plant in my 
study, which from being cooler than the hot-house was 
not very favourable for the experiment. The extremity 
was gently rubbed four or five times with a thin stick, 
and this was done as often as it was observed to have 
become nearly straight again after having been in 
action ; and in the course of 54 hrs. it answered to the 
stimulus 21 times, becoming each time hooked or 
spiral. On the last occasion, however, the movement 
was very slight, and soon afterwards permanent spiral 
contraction commenced. No trials were made during 
the night, so that the tendril would perhaps have 
answered a greater number of times to the stimulus ; 
though, on the other hand, from having no rest it 
might have become exhausted from so many quickly 
repeated efforts. 
