68 



MOEPHOLOGT, OR COMPARATIVE ANATOMY. 



which weak-stemmed plants attach themselves to foreign bodies. 

 They may be modifications of any part of the leaf or of a branch. 



In Lathyrus the blade-structure of the leaf is more or less deficient in 

 different species. In L. Apliaca (fi. 113) it is wholly wanting, the 

 petiole running out into a tendril, which may be regarded as consisting 

 either of the leaf-stalk alone, or of this and the midrib of the lamina. In 

 L. odoratus (Sweet Pea) the pinnately compound leaf has one pair of 

 leaflets, and usually one pair of tendrils, and a terminal tendril in the 

 ordinary place of the remaining leaflet. In the edible garden Pea there 

 are several pairs of leaflets, and often several pairs of tendrils, with a 

 terminal one. In Gluriosa superba, a Liliaceous plant, the broad simple 

 lamina runs out into a terminal tendril (fig. 114). In Smilax (fig. 115) 

 the two stipules are represented by a pair of tendrils ; while in the 

 Cucurbitacese one tendril only occurs, which some regard as a stipule, 

 others as a metamorphosed leaf, others, again, as a branch or peduncle. 



Fig. 116. 



Fig. 115. 



-Fig. 115. Tendrils ofSwilax aspera, formed from the stipules. 

 Fig. 116. Leaves and t- ndrils of the Vine. 



The tendrils of the Vine (tig. 116) are modified flowering branches, 

 originally terminal but displaced during growth so Fi<>-. 117. 



as to become placed opposite to leaves, and often 

 tuberculated by the existence of abortive flower- 

 buds. The nature of the axillary tendrils of Passion- 

 flowers is similar. 



Spines (spinai) or thorns are hard, sharp - 

 pointed woody processes, formed, like tendrils, 

 by modification of entire organs or parts of such. 



Thus in the common Berberry some of the leaves 

 are Represented by compound spines, in the axils of 

 which arise fasciculate groups of leaves. In the 

 False Acacia-tree (Robinia Pseudacaoia) the stipules 

 are represented by a pair of spines at the base of the 



petiole (fig. 117), while in certain species of Astra ^.-. F 



galus the petioles are converted into spines after the fall of their leaflets. 



Base of the leaf of Ho- 

 binia, with stipules de- 

 veloped as spines. 



