Chap. IV. SDMMAEY. 173 



by a touch of equal force on opposite sides, did not 

 bend. The inferior and lateral surfaces of the tendrils 

 of Mutisia are sensitive, but not the upper surface. 

 With branched tendrils, the several branches act 

 alike; but in the Hanhurya the lateral spur-like 

 branch does not acquire (for excellent reasons which 

 have been explained) its sensitiveness nearly so 

 soon as the main branch. With most tendrils the 

 lower or basal part is either not at all sensitive, or 

 sensitive only to prolonged contact. We thus see 

 that the sensitiveness of tendrils is a special and 

 localized capacity. It is quite independent of the 

 power of spontaneously revolving ; for the curling of 

 the terminal portion from a touch does not in the least 

 interrupt the former movement. In Bignonia unguis 

 and its close allies, the petioles of the leaves, as well 

 as the tendrils, are sensitive to a touch. 



Twining plants when they come into contact with a 

 stick, curl round it invariably in the direction of their 

 revolving movement; but tendrils curl indifferently 

 to either side, in accordance with the position of the 

 stick and the side which is first touched. The clasping 

 movement of the extremity is apparently not steady, 

 but undulatory or vermicular in its nature, as may be 

 inferred from the curious manner in which the tendrils 

 of the Echinocystis slowly crawled round a smooth 

 stick. 



As with a few exceptions tendrils spontaneously 

 revolve, it may be asked, why have they been endowed 

 with sensitiveness ? why, when they come into contact 



