80 MR. DARWIN ON CLIMBING PLANTS. 



which diverge equally from it. One of the branches (B) has 

 a scale at its base, and is always, as far as I have seen, Longer 

 than the other, and very often bifurcates. The several branches 

 when rubbed become curved, and subsequently straighten them- 

 selves. After a tendril has clasped any object by its extremity, 

 it contracts spirally ; but this does not occur (Palm, S. 5(>) when 

 no object has been seized. The tendrils move spontaneously from 

 side to side ; and on a very hot day one made two elliptical revo- 

 lutions at an average rate of 2 h. 15 m. During these movements 

 a coloured line, painted along the convex surface, became first 

 lateral and then concave. The separate branches have inde- 

 pendent movements; after a tendril has spontaneously revolved 

 for a time, it bends from the light towards the dark : I do not 

 give this latter statement on my own authority, but on that of 

 Mohl and Dutrochet ; Mohl (S. 77) says that in a vine planted 

 against a wall the tendrils point towards it, and in a vineyard 

 generally more or less to the north. 



The young internodes spontaneously revolve ; but in hardly any 

 other plant have I seen so slight a movement. A shoot faced a 

 window, and I traced its course on the glass during two perfectly 

 calm and hot days ; during ten hours on one day it dcscrihed a 

 spire, representing two and a half ellipses. I likewise placed a 

 bell-glass over a young muscat grape in a hothouse, and it made 

 three or four extremely minute oval revolutions each day: the 

 shoot moved less than half an inch from side to side ; and had it 

 not made at least three revolutions during the same day when the 

 sky was uniformly overcast, I should have attributed the motion 

 to the varying action of the light. The extremity of the shoot is 

 more or less bent downwards; but the extremity never reverses 

 its curvature, as so generally occurs with twining plants. 



Various authors (Palm, S. 55; Mohl, S. 45; Lindley, Mr.) 

 believe that the tendrils of the vine are modified flower-peduncles. 

 I here give a drawing (fig. 10) of the ordinary state of a flower- 

 peduncle in bud: it consists of the "common peduncle" (A); of 

 the "flower-tendril" (B), which is represented as having caught 

 a twig; and of the "sub-peduncle" (C) bearing the flower-buds. 

 The whole peduncle moves spontaneously, like a true tendril, but 

 in a less degree, and especially when the sub-peduncle (C) does 

 not bear many flower-buds. The common peduncle (A) has not 

 the power of clasping a support, nor has the corresponding part 

 in the true tendril. The flowei'-tcndril (B) is always longer than 

 the sub-peduncle (C), and has a scale at its base ; it sometimes 



