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. 



P ro J ect re PeUmgly from some 



FIG. is.-Tendriis trans- 

 formed from leaf-blades, kinds of plants as if they might form a 



with stipular foliage, of . , i r i 



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

 plant-eating 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- 



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 



