CLIMBING PLANTS 



119 



tion is taken over by the stipules, which are large and 

 leaf -like. 



(ii.) Stipules. In Smilax (sarsaparilla), a climber fre- 

 quently seen in greenhouses, the tendrils are in the posi- 

 tion of stipules. Climbing hooks may also be present. 



(iii.) Leaf -Tips. In the climbing lily (Gloriosa superba), 

 another foreign greenhouse-plant, the tips of the leaves 

 are prolonged into strong cord-like tendrils. 



(iv.) Petioles. The garden - nasturtium (Tropceolum 

 ma jus) and Clematis have sensitive leaf -stalks. On reach- 

 ing a support, they curve round it, and then become 

 tough and indurated, thus enclosing it 

 firmly. 



4. Root - Climbers. These climb by 

 adventitious roots, which arise in great 

 number on the shaded side of the stem. 

 They act as suckers, pinning the branches 

 to the wall or to the tree up which the 

 plant climbs e.g., ivy (Hedera Helix). 

 No suckers, however, occur on the 

 flowering shoots, which turn away from 

 the wall and grow outwards towards the 

 light. 



In many plants the morphological 

 nature of the tendril is doubtful. In the 

 vegetable-marrow (Cucurbita), cucumber 

 (Cucumis), white bryony (Bryonia dioica), 

 and other Cucurbitaceae, the tendrils have 

 been variously described as modified 

 leaves, stipules, shoots, and even roots. 

 It is possible, however, that in these 

 cases the tendrils are not modified forms 

 of other organs at all, but are organs, sui generis (Latin, 

 of their own kind) that is, organs which have arisen 

 and have been developed for the purpose which they 

 serve, never having been anything else but what they are. 



Climbing plants begin their existence as deep-shade 

 plants, the shade being produced by the vegetation upon 

 which they climb. In the Tropics most are inhabitants 

 of forests ; in this country they are found in thickets and 

 hedges. Here the partial light produces effects which 

 are ordinarily associated with plants grown in darkness. 

 Such plants have a long weedy appearance, with weak 



FIG. 37. STEM- 

 TENDRILS OF 

 Ampelopsis 

 Veitchii, SHOW- 

 ING SUCKERS. 

 (REDUCED.) 



