TWINING OF TENDRILS. 



865 



sap. The direct action of light is not necessary for twining, since even etiolated plants 

 (as Ipomcea purpurea and Phaseolus multiflorus) cling closely to their support in the dark. 

 The assertion of Duchartre that Dioscorea Batatas does not twine in the dark reduces 

 itself, according to de Vries's more recent observations, to the fact that while normal 

 green shoots continue to climb in the dark, they cease rotating and twining when they 

 become etiolated. 







^^comprised all filiform or at least slender long and narrow parts of plants which 

 possess the property of curving round slender solid supports with which they come 

 in contact during their growth, clinging to them in consequence, and thus at length 

 fixing the plant to them. Tendrils are therefore at once distinguished from climbing 

 internodes by their irritability to contact or pressure. 



Organs of the most various morphological description may assume this physi- 

 ological property. Sometimes tendrils are metamorphosed branches, as in Vih'Sf 

 Ampelopsi's, Passiflora, and Cardiospermum Halicacabum, where they may be con- 



»_ sidered more accurately as metamorphosed flower-stalks or inflorescences. In 



Fig. 486.— Mode of climbing of Tropceolum minus. The long petiole a of the leaf / is sensitive to 

 long-continued contact, and has clung round a support and round the stem of the plant itself j/ so as to 

 fix this stem firmly to the support ; z the shoot from the axil of the leaf. 



^MCuscuia the whole stem may be regarded as a tendril rather than as a climbing 

 stem. In other cases, as in Clematis^ Tropceolum (Fig. 486), Maurandia, Lopho- 

 spermum, Solatium jasminoides, &c., the petioles may serve as tendrils. In Fu- 

 maria officinalis and Corydalis claviculata the whole of the finely-divided leaf is 

 sensitive to contact, and its separate parts have the power of twining round slender 

 bodies. In Gloriosa Planiii and Flagellaria indica the mid-rib protruding beyond 

 the leaf serves as a tendril. In many Bignoniacese, in Cobcea scandens, in Pisum, 

 &c. the anterior (upper) part of the pinnate leaf is transformed into slender filiform 

 tendrils inclined forwards, while the basal part of the leaf is rigid and divided 

 into leaflets ; sometimes, as in Lathyrus Aphaca^ the whole of the leaf is replaced 

 by a fiUform tendril. The morphological character of the tendrils of Cucurbi- 

 taceae is still doubtful, though they must probably be regarded as metamorphosed 

 branches. 



' ^ See the literature quoted in the preceding section, and de Vries, Arb. d. hot. Inst, in 

 Wiirzburg, I. 



3 K 



