THE ORGANOGRAPHY OF TENDRILS. 



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more by the fact that when ihey arc young and first project from the leaf-lnid of llie 

 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. c. ihcy are not coiled up. 



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 Cleviatis, in the Indian Cress ( Tropcrohini), Maiiraiidia, 

 Lophospermtim, Solanum jasmmoides, &c., the petiole itself acts as a tendril, as shown 

 in Fig. 376; in the common Fumitory [Fumaria officinalis) and the allied Corydalis 

 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 Ghriosa Blandii and FlagcUaria 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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