1{)4 MB. DABWm 01^ CLniBTKG PLANTS, 



traction into a firm bundle. In the Cob (^a the tendrils alone 

 revolve ; these are divided into many fine branches, terminating 

 in sharp little hooks, which crawl into crevices, and are turned by 

 ail excellently adapted movement to any object that is seized. In 

 the Ampelopsis, on the other hand, there is little or no power of 

 revolving in any part : the branched tendrils are but little sen- 

 sitive to contact ; their hooked extremities cannot seize any thin 

 object ; they will not even clasp a stick, unless in extreme need 

 pf a support ; but they turn from the light to the dark, and, 

 spreading out their branches in contact with any nearly flat sur- 

 face, the disks are developed. These can adhere, by the secretion 

 of some cement, to a wall, or even to a polished surface ; and this 

 is more than the disks of the Bignonia ca^reolata can effect. • 



The formation and rapid growth of these adherent disks is one 

 of the most remarkable peculiarities in the structure and functions 

 of tendrils. We have seen that such disks are formed by two 

 ; species of JBignonia^ by the Ampelopsis, and, according to Naudin*, 

 by the Cucurbitaceous genus Peponopsis adliwrens. Their deve- 

 lopment, apparently in all cases, depends on the stimulus from 

 . contact. It is not a little singular that three families so widely 

 distinct as the Bignoniacese, Vitacese, and Cucurbitacese should all 

 have species bearing tendrils with this same remarkable pecu- 

 liarity. Most tendrils, after they have clasped any object, rapidly 

 increase in strength and thickness throughout their whole length ; 

 : but some tendrils, when wound round a support either by the 

 middle or the extremity, become swollen at these points in a 

 j-remarkable manner ; thus I have seen the clasped portion of a 

 t^endril of the Bignonia Chamberlaynii grown twice as thick as the 

 free basal portion, and become wonderfully rigid. In the An- 

 guria 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 ; in the Ilanhurya a similar layer is developed, 

 ^ which is adherent ; lastly, in the Peponopsis adherent disks are 

 : formed at the tips of the tendrils. These three last-named genera 

 ; belong to the Cucurbitacese, so that, in this one family, we have a 

 nearly perfect gradation from a common tendril to one that forms 

 : an adherent disk at its tip 5 the one small step which is wanted is 

 a^tendril in a state between that of the Anguria and Hanhurga 

 that is, adherent only in a slight degree or occasionally. 



Finally, it may be added that America, which so abounds with 

 arboreal animals, as has lately been insisted on by Mr. Bates, 



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



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