170 TENDBIL-BEAllEES. Chap. IV. 



the intemodes and tendrils re^Dlre together at the 

 same rate ; in Cissus, Cobaea, and most PassifloriB, the 

 tendrils alone revolye ; in other cases, as with Lathyrus 

 aphaca, only the internodes move, carrying with them 

 the motionless tendrils; and, lastly (and this is the 

 fourth possible case), neither intemodes nor tendrils 

 spontaneously revolve, as with Lathyrus grandiflorus 

 and Ampelopsis. In most Bignonias, Eccremocarpus, 

 Mutisia, and the TumariaceEe, the internodes, petioles 

 and tendrils all move harmoniously together. In 

 every case the conditions of life must be favourable in 

 order that the different parts should act in a perfect 

 manner. 



Tendrils revolve by the curvature of their whole 

 length, excepting the sensitive extremity and the 

 base, which parts do not move, or move but little. 

 The movement is of the same nature as that of the 

 revolving intemodes, and, from the observations of 

 Sachs and H. de Vries, no doubt is due to the same 

 cause, namely, the rapid growth of a longitudinal band, 

 which travels round the tendril and successively bows 

 each part to the opposite side. Hence, if a line be 

 painted along that surface which happens at the time 

 to be convex, the line becomes first lateral, then 

 concave, then lateral, and ultimately again convex. 

 This experiment can be tried only on the thicker 

 tendrils, which are not affected by a thin crust of 

 dried paint. The extremities are often slightly curved 

 or hooked, and the curvature of this part is never 

 reversed ; in this respect they differ from the ex- 



