56 PENHALLOW ON MECHANISM 
Coils 2, 3, 4, 5 could not be fully straightened for measurement, allowance for which 
had to be made. Thus if we add to the above numbers as follows : 1.0, 3.0, 5.0 and 1.0 em. 
respectively, we then get as the total lengths of all the tendrils, 12.5, 7.6, 10.3, 15.1 and 
16.5 em. We thus get as the extreme range in elongation, from 50 per cent. to 100 per 
cent. of the original length, and the mean ratio of increase would be as 1 : 1.14, showing 
that the tendril at least doubles in length after the uncoiling from the bud, and during 
the period of circumnutation. 
Co1LInG.—When brought in contact with an object near the tip, the tendril, at once 
affected by the irritation, coils about the support with a firm grasp. The effect of irrita- 
tion does not immediately extend along the remainder of the tendril, as is shown by the 
fact that, when the tip is brought in contact, the basal portion of the tendril continues its 
movement and passes by as a curve, the sensitive surface thereby becoming convex instead 
of concave, as would occur if it felt the influence of contact. After a time, however, the 
effect of contact extends to all the cells of the basal portion, which then draws itself into a 
closer and closer spiral. When brought in contact with an object, the tendril does not 
immediately lose its power of nutation, but often retains it for a very considerable period, 
this being dependent upon the age of the tendril, and especially upon the particular 
state of lignification in the bast. It becomes evident, therefore, that when the tip is 
arrested, the bands of vibrogen, still continuing to act in the basal portions, tend to bow 
the tendril in all directions as before. Their power to do so being modified by fixation of 
the tip, the natural result would be for the centre to pass by the point of support as a curve 
having the sensitive side outermost. Continued circumnutation of the free central portion 
between two fixed extremities must result in torsion, which will be right or left hand as 
the case may be, from both ends towards the centre, and when such torsion becomes exces- 
sive, its compensation is of necessity found in a double spiral ', which always characterizes 
the fixed tendril. If coiling in the free central portion were primarily due to the irrita- 
tion of contact, we should expect to find the coiling first developed as the direct result of 
simple contraction along one side, and this would not immediately give rise to torsion. 
Tendrils which have not suffered contact, always coil upon themselves at the completion 
of their period of circumnutations. Such coils, however, are always somewhat loose and 
quite irregular, and are the direct result of excessive inequality of tension between the 
bast and vibrogen, therefore of unequal maturity in the tissues. 
CIRCUMNUTATION.—The circumnutations of the tendrils commence as soon as each 
arm uncoils from the bud condition. The central and largest arm generally uncoils first, 
and later, the laterals. The whole period of circumnutation in a rapidly growing vine, 
under favorable circumstances, is usually about two days—rarely three days. During 
this period, the motion is at first by grand and regular sweeps, but it gradually becomes 
slower as the end is reached ; and in the later periods, the movement is spasmodic, often 
exhibiting rest periods alternating with those of great activity. Ultimately the end is 
reached in the formation of a spiral, which is more or less loose and irregular if free, or 

' Darwin, Climbing Plants, 163, etc. 
