CHAP. II. 



LEAVES. 



119 



a lid termed the operculum. To me it appears that the pitclier 

 itself, or fistular part, is the petiole, and the operculum the 

 blade of a leaf in an extraordinary state of transformation. 

 Look, for example, at Dioneea muscipula ; in this plant the 

 leaf consists of a broad- winged petiole, articulated with a col- 

 lapsing blade, the margins of which are pectinate and 

 inflexed. Only suppose the broad-winged petiole to collapse 

 also, and that its margins, when they meet, as they would in 

 consequence of a collapsion, cohere ; a fistular body would 

 then be formed, just like the pitcher of Sarracenia {Ju/. 58. B), 

 and there would be no difficulty in identifying the acknow- 

 ledged blade of Dionaea with the operculum of Sarracenia 

 also. From Sarracenia the transition to Nepenthes {Jig. 58. A) 

 would perhaps not be considered improbable. 



59 



The student must not, however, suppose that all pitchers 

 are petioles, because those of Nepenthes and Sarracenia are 

 so. Those of the curious Dischidia Rafflesiana {Ji<j. 59.), 

 figured by Wallich in his PlantcB Asiaticce Rariores, are 

 leaves, the margins of which are united. The pitchers of 

 Marcgraavia and Norantea {Jig. 60.) are bracts in the same 

 state. 



SpiJies oj the leaves are formed either by a lengthen- 

 ing of the woody tissue of the veins, or by a contraction 



I 4 



