64 



LEAVES. 



[section 7. 



a large and very sliowy petal-like leaf ; the original dry scale is apparent 

 iu the uotcli at the apex. 



1G7. Leaves as Spines occur in several plants. A familiar instance is 

 that of the common Barberry (Fig. 171)- In almost any summer shoot, 

 most of the gradations may be seen between the ordinary leaves, with 

 sharp bristly teeth, and leaves which are reduced to a branching spine or 

 thorn. The fact that the spines of the Barberry produce a leaf-bud in 

 their axil also proves them to be leaves. 



168. Leaves for Climbing are various in adaptation. True foliage- 

 leaves serve this purpose ; as in Gloriosa, where the attenuated tip of a sim- . 

 pie leaf (otherwise like that of a Lily) hooks around a supporting object ; 

 or in Solanum jasminoides of the gardens (Fig. 172), and in Maurandia, 

 etc., where the leaf-stalk coils round and clings to a support ; or iu the 

 compound leaves of Clematis and of Adlumia, iu which both the leaflets 

 and their stalks hook or coil around the support. 



169. Or iu a compound leaf, as in the Pea and most Vetches, and in 

 Cobsea, w'hile the lower leaflets serve for foliage, some of the up])ermost 

 are developed as tendrils for climbing (Fig. 167). In the common Pea this 

 is so with all but one or two pairs of leaflets. 



170. In one European Vetch, the leaflets are wanting and the whole 

 petiole is a tendril, while the stipules become the only foliage (Fig. 173). 



171. Leaves as Pitchers, or hollow tubes, are familiar in the common 

 Pitcher-plant or Side-saddle Flower (Sarracenia, Fig. 174) of our bogs. 

 These pitchers are generally half full of water, in which flics and other in- 

 sects are drowned, often in such numbers as to make a rich manure for the 

 plant. More curious are some of the southern species of Sarracenia, which 

 seem to be specially adapted to the capture and destruction of flies and 

 other insects. 



Fig. 172. Leaves of Solainini jasminoides, the petiole adapted for climbing. 

 Fig. 173. Leaf of Lathyrus Apliaca, consisting of a pair of stipules and a tendril. 



