142 
ORGANOGRAPHY. 
BOOK I. 
green body, occupying the place and performing the functions 
of a leaf, and closed at its extremity by a lid, termed the 
operculum. The pitcher, or fistular part, is the petiole, and 
the operculum the blade of a leaf in an extraordinary state 
of transformation. This is found, by a comparison of Ne- 
penthes and Sarracenia with Dionaea muscipula; in that 
plant the leaf consists of a broad-winged petiole, articulated 
with a collapsing blade, the margins of which are pectinate 
and inflexed. If we suppose the broad-winged petiole to 
collapse, and that its margins, when they meet, cohere, 
there would then be formed a fistular body like the pitcher 
of Sarracenia {Jig. 58. B), and there w^ould be no difficulty 
in identifying the acknowledged blade of the one with the 
operculum of the other. From Sarracenia the transition to 
Nepenthes (Jig. 58. A) is obvious. 
The student must not, however, suppose that all pitchers 
are petioles, because those of Nepenthes and Sarracenia are 
so. Those of the curious Dischidia llafflesiana (fig. 59.), 
figured by Wallich in his Plant(B Asiaticce Bariores, are leaves, 
the margins of which are united. The pitchers of Marcgraavia 
and Norantea (fig. 60.) are bracts in the same state. 
Spines of the leaves are formed either by a lengthening of 
the woody tissue of the veins, or by a contraction of the 
59 
