Chapter IV — 61 — Nepenthes 



basal part is composed of two halves which separate above and now 

 appear as the wings on the adaxial pitcher wall to form a transverse 

 membrane below the rim (Hooker, Dickson, Macfarlane). When 

 the transverse connection is absent (which Goebel held to be the case), 

 there is often an indication of it in the presence of a row of gland-like 

 emergencies indicating such a connection (Stern observed such). 

 Macfarlane said that a transverse strand of the venation also is to be 

 taken as an indication, but I cannot substantiate this (7 — 7, 9). 

 Hooker's view that the pitcher is "the hollowed out upper half of the 

 petiole" is discarded, and Dickson's theory of contracted peltate leaf 

 blade accepted. The earlier embryological condition is now examined. 

 In an early stage, when the leaf appears as a low conical structure, 

 there is a pit just below the apex on the adaxial side. Just below it is a 

 transverse weal, the transverse connection of the edges of the leaf base. 

 The leaf blade, it is important to note, arises on the abaxial side of 

 the leaf base, the latter, as in Iris, presenting total stipulation. The 

 blade cannot therefore be an extension of the apex of the stipule, but 

 though near it must arise below, abaxially. If without further differ- 

 entiation this embryonic stage passes into permanent form, a primary 

 leaf results, in which the pitcher stands in a dorsal position. What 

 authors have designated the blade is therefore only the leaf base 

 showing total stipulation, of which the transverse sector, as already 

 said, may be suppressed. In support of this I may point out that the 

 extent of the pitcher wings is not commensurate with that of the 

 veins beneath them, the wings often extending beyond the venation, 

 which swerves away to pass around the mouth of the pitcher. This 

 in the adult leaf. In intermediate forms, the development of the 

 rudiments proceeds further, especially the tendril, by contraction be- 

 low the pitcher. Nevertheless the wings of the pitcher pass down 

 along the edges of the tendril. In purely adult forms the tendril be- 

 comes entirely wingless. Troll now asks: (7) May the tendril be re- 

 garded as the petiole of the leaf between the pitcher as blade and 

 the leaf base? (2) How are the wings of the pitcher to be understood? 

 To answer these he analyzes the embryonic condition. In this a peti- 

 ole is not recognizable as such, but assuming that it must be there, he 

 postulates a zone of tissue, broad abaxially and narrow or absent 

 adaxially, the narrow adaxial edge of this wedge of tissue impinging 

 on the leaf base at its transverse weal (Wulst). The elongation of 

 this petiolar zone meets, however, an impediment in the leaf base tis- 

 sues, which converge below the mouth depression. In consequence, the 

 leaf base is dragged out along with the petiole and adaxial side of the 

 pitcher up to the edge of the mouth (but not quite, it may be added). 

 The whole adaxial side of the young leaf from the leaf base to the 

 mouth (I should say not quite) belongs to the leaf base and one may 

 come to the view that the tendril is an extension of the leaf base as 

 Goebel showed to be the case for the fan-palms. Nevertheless Troll 

 insists that the tendril is a petiole, though it may in some instances 

 (such as ;V. clipeata) have an unifacial structure in the lower portion. 

 But the leaf base is never unifacial, always bifacial. But where the 

 tendril is bifacial it should be regarded not as entirely independent 

 indeed, but concrescent with the leaf base. 



