PLANTS OF HEDGEROWS AND WALLS 341 



(c) Twining stems, twining either 



(a) to right or left indifferently Woody Night- 

 shade. (Also by means of its leaf-stalks.) 



(b) clockwise (i.e. left to right or with the sun) 

 Hop, Black Bryony (Fig. 90), and Honey- 

 suckle. 



(c) Contra-clockwise (i.e. right to left or against 

 the sun) Bindweeds. 



(d) Sensitive organs (tendrils) : 



(a) Branch tendrils White Bryony (Bryonia 

 dioica) (Fig. 91). 



(b) Leaf-stalk tendrils Clematis (Fig. 92). 



(c) Leaflet tendrils Bush Vetch (Fig. 220) and 

 Climbing Fumitory. 



The Ivy is well adapted to the conditions of life in a 

 hedgerow or wood, and possesses many points of interest. 

 If its long slender branches spread out on the ground the 

 leaf-blades face upwards. Commonly the branches climb 

 the trunks of trees by pressing their groups of adventitious 

 roots into irregularities of the bark, where they adhere 

 firmly and serve as holdfasts (Fig. 222, 1). The leaves arise 

 spirally on the axis, and in their broad bases the buds 

 are partly embedded. The leaf -bases are sensitive motile 

 organs, and a very slight movement in this region carries 

 the blades at the ends of their long stalks through a wide 

 arc away from the shade towards the light ; by further 

 movement at the top of the leaf-stalk the blades are so 

 placed in relation to each other as to form good leaf -mosaics, 

 and the tips all point downwards. The upper surface of 

 the blade is glossy and concave, and the drainage-channels 

 are directed towards the apex, which serves as a ' drip-tip ' ; 

 thus rain and snow quickly drain away. Observe the 

 behaviour of the shoots which overtop the tree-trunk or 

 a wall and thus lose support and shade. On such shoots 



