20 « J« M. Macfarlane. — Nepenthaceae. 



The histology of the lid or operculum in the different species closely agrees, the 

 greatest featui'e of Variation being the relative amount and character of the hairs. But 

 the internal surface often presents features of great morphological and taxonomic im- 

 portance. In N. ampullaria alone the elliptic rudimentary lid has as a rule no attrac- 

 tive lid glands, though in large richly colored examples from Singapore and Borneo an 

 occasional gland may be detected. In all others the lid glands are either fairly or 

 very abundant, and as a rule secrete freely in young fresh pitchers. In N. Hookeriana 

 N. Rafflesiana and N. Northiana the glands are mainly or wholly disposed in two 

 longitudinal scries between the middle line and the margins of the lid. In the majority 

 of species they are largest and most thickly massed along the middle. In such species 

 as N. maxima and N. Boschiana that have basal keels to the lids, the keels are 

 richly paved with large glands. In N. bicalcarata and N. Burbidgei numerous glands 

 of moderate size are uniformly distributed over the entire lid. In most cases the gland 

 tissue is almost flat, and is directly exposed (Fig. 7 -ff) or slightly covered by a down- 

 growing epidermal Aap , but in N. gracilis, N. Lowii and N. Pervillei (Fig. 7 G) the 

 glands are almost identical with those of the lamina, and similarly open by a small 

 circular orifice. Those of N. Lowii are relatively gigantic (Fig. 7 D) and are deeply em- 

 bedded in the thick substance of the lid. 



Histologically and physiologically, the pitcher cavity shows two diverse conditions 

 in some species, that are connected by all gradation forms in other species. In a 

 considerable number, typified by N. Lowii, N. ampullaria, N. Burbidgei and N. bi- 

 calcarata (Fig. \ 4), the entire cavity is lined by a greatly cuticularized glistening and 

 smooth epidermis, that has glands uniformly distributed over it. This can appropriately 

 be called the "detentive" (detinens) and digestive surface, since physiologically it fulfils 

 the funetions of preventing the escape of caught insects, of pouring out a digestive 

 liquid when the glands are stimulated, and of absorbing the digested producls of animal 

 tissues. Very different is the relation in such species as N. alata, N. Reinwardtiana, 

 N. gracilis (Fig. 4) and N. khasiana, where the lowermost half or one-third is 

 detentive, while the upper area from the rim to the top of the last-named region is 

 usually glaueous, glaucous-purple or purple, in part due to a waxy surface secretion 

 in part to an epidermal pigment. It is extremely smooth and ill-adapted for free 

 insect movements. Further, it is closely covered by many transversely placed ledge- 

 like cells (Fig. 8 C) that are raised slightly above the epidermal surface. These ledges 

 represent transversely placed stomata, which in embryonic pitchers have a normal 

 stomatic aspect. But gradually the lower of the two guard cells sinks inward behind 

 the upper, so that the former and the stomatic orifice become hid by the exerescent 

 and parallel position of the outer cell. This area may well be named the "condueting" 

 (deducens) surface, since it affords no sure foothold for insects, but rather conduets 

 or drops them into the lower part. In such species as N. Macfarlanei and N. Ro- 

 ivanae it may not extend over more than one-eighth to one-fifth the depth of the 

 pitcher. Where distinctly dimorphic basal and cauline pitchers are developed, as in N. 

 Rafflesiana and N. melamphora, the former may be wholly glandulär, the latter glandulär 

 below and condueting above to one-sixth or one-third of its depth. 



The glands of the detentive surface are almost identical in strueture with those 

 of the lid, though they differ greatly in funetion. In some species, or in large pitchers, 

 they may be relatively large. Thus in mature pitchers of N. Lowii the upper glands 

 are of small size, are widely apart, and are completely covered by downwardly directed 

 epidermal flaps. Gradual transitions from these can be traced to glands at the bottom 

 of the pitcher that may be huge quadrangular or polygonal masses separated from eacli 

 other by ridges of thick-walled epidermal cells (Fig. 8 E). As compared with typical lid 

 glands the detentive ones are usually covered by a shallow to deep epidermal and cuticular 

 flap (Fig. 8ffe) that may partially or wholly cover the gland. In the geographically widely 

 separated species N. Pervillei and N, Vieillardii the flap is so largely developed as to 

 form a deep pocket with narrowed mouth (Fig. 8D). The epidermal and subepidermal 



