THE ORGANOGRAPHY OF TENDRILS. 



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more ty fhe fact'that when they are young and first project from the leaf-bud of the 

 shoot, they are closely rolled together in the form of a helix, and this in such a way 

 that their outer side is convex ; only on further development does the helix uncoil 

 itself, progressively upwards from the lower part of the tendril, until it is approxi- 

 mately straight along its whole length. The tendrils of other plants are more or less 

 straight from the beginning — i. e. they are not coiled up. 



Fig. 375.— a shoot j4 of the White Bryony {Bryonia dioica) climbing by means of tendrils abed. 

 S a dry twig serving as a support. 



In the examples quoted we have true typical tendrils. In other cases, however, 

 it is peculiarly developed parts of leaves, specially endowed with irritability and 

 more or less filiform and sensitive to contact, which assume the chief properties of 

 tendrils. In many species of Clematis, in the Indian Q,x&%'& (Tr'opaolurri), Maurandia, 

 Lophospermum, Solanum jasminoides, &c., the petiole itself acts as a tendril, as shown 

 iii Fig. 376; in the common Fumitory (Fuiriaria officinalis) shA the allied Corj/t/a/w 

 claviculata, ihe whole of a leaf is branched into fine slender filaments, and is irritable 

 to contact and able to twine its separate parts round thin bodies. In the case 

 of Gloriosa Blandii and Flagellaria Indica the midrib projects beyond the apex of 

 the broad simple lamina and serves as a tendril; and similarly with the Pitcher-plants 



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