54: D. P. Penhallow — Tendril Movements in 



describes a figure, the vertical plane of which is parallel with 

 the axis of the plant, the space through which the tip moves is 

 greatly augmented by a supplementary movement in the grow- 

 ing end of the vine, on which the tendril is found. This sec- 

 ondary movement causes the tendril tip to describe a double 

 movement which increases the possibility of contact with sur- 

 rounding objects.* It is of short duration, however, since the 

 movement of the vine is confined to the few internodes at the 

 end, and at any one node, continues for about two days only, 

 after the tendrils are in motion ; so that by the time the first arm 

 of the latter has grasped a support, the movement of the vine 

 at that particular node may have ceased entirely. So long as 

 there is no contact with a suitable support, which must be of a 

 size easily grasped by the coils, the tendril continues to revolve 

 until a gradual increase of woody tissue arrests its activity. 

 Toward the close of its movements, the tendril often falls to 

 the ground and remains there for some time, or commences to 

 coil upon itself, only to straighten out once more and resume 

 its nutations. This may happen several times at decreasing 

 intervals as the tendril grows older, until finally, the whole 

 arm coils upon itself in a simple spiral with the coils turning 

 outward, becomes hard and woody and its functions then cease 

 entirely. - }" 



When brought in contact with an object near the tip, the 

 latter, at once affected by the irritation, coils about the support 

 with a firm grasp. The effect of irritation does not imme- 

 diately extend along the remainder of the tendril, as is shown 

 by the fact that when the tip is brought into 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 a tendril comes in contact with an 

 object, it does not immediately lose its power of nutation, but 

 retains it for a very considerable period, and this is largely de- 

 pendent upon and influenced by the age of the organ, retention 

 being longer in the young and vigorous than in the more aged. 

 It becomes apparent, therefore, that when the tip is arrested, 



* The fact that there is this double motion as a resultant of tendril vine action, 

 shows that the true figure is to be obtained only when the tendril revolves about 

 the inner surface of a glass globe and the changes of direction are recorded from 

 the outside. This, however, was not practicable in our case, nor was it essential 

 to the accuracy of the conclusions to be obtained, as will be seen later. For our 

 purpose, the plane recording surface was amply sufficient. 



f My observations upon this point confirm those of Darwin with regard to other 

 members of Cucurbitacece, that when a spiral is developed freely, it is always 

 simple ; that it only reverses when the tip is attached to a support. 



