Chap. IV. SUMMAEY. 179 



These adhere by the secretion of some cement to a 

 wall, or even to a polished surface ; and this is more 

 than the discs of the Bignonia capreolata can effect. 



The rapid development of these adherent discs is 

 one of the most remarkable peculiarities possessed by 

 any tendrils. We have seen that such discs are formed 

 by two species of Bignonia, by Ampelopsis, and, 

 according to Naudin,* by the Cucurbitaceous genus 

 Pejjonopsis adhserens. In Anguria the lower surface of 

 the tendril, after it has wound round a stick, forms 

 a coarsely cellular layer, which closely fits the wood, 

 but is not adherent ; whilst in Hanburya a similar 

 layer is adherent. The growth of these cellular out- 

 growths depends, (except in the case of the HayAolopliium 

 and of one species of Ampelopsis,) on the stimulus from 

 contact. It is a singular fact that three families, so 

 widely distinct as the Bignoniacea?, Yitacese, and 

 Cucurbitaceae, should possess species with tendrils 

 having this remarkable power. 



Sachs attributes all the movements of tendrils to 

 rapid growth on the side opposite to that which 

 becomes concave. These movements consist of re- 

 volving nutation, the bending to and from the light, 

 and in opposition to gravity, those caused by a touch, 

 and spiral contraction. It is rash to differ from so great 

 an authority, but I cannot believe that one at least of 



* Annales des Sc. Nat. Bot. 4th series, torn. xii. p. 89. 



