68 



The Living Plant 



which makes a turn around some object, as in the Clematis, or 

 a cylindrical part between two portions of blades as in those 

 Pitcher plants called Nepenthes (figure 20). In some tropical 



plants, e. g., climbing Aroids, the aerial 

 roots clasp horizontally around a support. 

 In some others, and notably those having 

 the habit of the Ivies, and growing against 

 stonework, the tips of the tendrils do not 

 twine around a support, but end in discs 

 which are firmly appressed to the stones, 

 as in the Woodbine, though more com- 

 monly the disc-holding structures are aerial 

 roots, as the English Ivy illustrates. 

 ,,, ^ , ., , Spines project repellingly from some 



Fiu. 18. — Tendrils trans- -^ i j i . 



formed from leaf-blades, kiuds of plauts as if they might form a 



with stipular foliage, of , , • • i ,^ , , i ft 



Lathyrus Aphaca; one-half protection agaiust the attacks of large 

 natura size. plaut-eatiug beasts. They possess a stiff, 



hard, conical structure, and a firm attachment to the skeleton, 

 consistent with that use. In some plants they are no more than 

 prickles, erupted, so to speak, from the surface, as in the Rose; 

 in other cases they are the sharp- 

 ened ends of the veins, as in the 

 Holly; in others they are the leaf- 

 blades, as in the Barberry and 

 the Cactus; in others they are 

 stipules as in the most spiny 

 of the Euphorbias (figure 19), 



though in some other kinds the Fig. 19.-The stipular spines of Euphorbia 

 spines are the persistent and in- ^plendens; one-half natural size. 



durated floral branches; in others, such as the Locusts, they are 

 transformed branches coming from ordinary axillary buds; in 

 some Palms they are roots ; and cases are known where they are 

 petioles. 



Food Reservoirs store up for later use the food-material made 



