126 Scientific Intelligence. 
the best condition, make almost hourly revolutions, and the Jong, delicate, 
straight tendrils revolve nearly in the same manner and at the same rate. 
The sensitiveness of the tendril, when full-grown, is correspondingly 
great, a single light touch on the concave surface of the tip causing a 
considerable curvature. “A loop of soft thread weighing yynd of a 
grain, placed most gently on the EPs thrice plainly caused it to curve, as 
twice did a bent bit of thin platinum wire weighing ath of a grain; 
from 25 to 39 seconds. After coiling into an open helix upon transient 
apsai they soon straighten “gain, eet: their sensibility ; but i 
left in contact, the action continue e found it a pretty experiment, 
last summer, during the earenant “days, to Sting the upper part of an 
outstretched tendril by its inner or concave side against a twig or cord, 
and to see how promptly it would clasp it, revolving its free apex round 
and round it. A curious discrimination in the sensibility of such ten- 
drils is mentioned by arwin, as follows :— 
“T repeated the cperlibent made on the reine and placed sey- 
eral plants of this Passiflora so close together that the tendrils were re- 
peatedly dragged over each other; but no curvature same I likewise 
repeatedly flirted small drops of water from a brush on many tendrils, 
and syringed others so violently that the whole tendril was dashed about, 
but they never became curved. The impact from the drops of water on 
my hand was felt far more plainly than that from the loops of thread 
{weighing j,nd of a grain) when allowed to fall upon it, and these 
oops, which caused the tendrils to become curved, had been placed m 
gently on them. ence it is clear, either that the tendrils are habitu- 
ated to the touch of other tendrils and to that of drops of rain, or that 
they are sensitive only to prolonged though excessively slight pressure. 
To show the difference in the kind of sensitiveness in different plants, and 
likewise to show the force of the syringe used, [ may add that the light- 
est jet from it instantly caused the leaves of a Mimosa to close; whereas 
the loop of thread weighing =4nd of a grain, when rolled into a ball and 
gently placed in the glands. at the bases of the leaflets of the Mimosa, 
caused no action.” 
Of es ir tendrils, the most active, after ins of Sicyos (soe 
r in ha: f i 
markable appearance of discrimination in tendrils is that which Mr. Dar- 
win first noticed in this plant, but which may be seen in others,—® —and 
which he thus describes :— 
repeatedly saw — the revolving tendril, though ibe during 
a greater part of its course at an angle of about 45° ne case of 
only 37°) above the ier in one part of its course ere and 
Seraiglitesi ‘aa from tip to base, and became nearly or quite vertical. . 
The tendril forms a very acute angle Mier the eatreisil of = 
the shoot, which ncaa above the point where the tendril arises; an° 
the stiffening always occurred as the tendril Scan and had to 
