Chapter IV — 65 — Nepenthes 



suggesting that the pocket may serve to hold a drop of nectar when 

 the pitcher is in active condition. In this species also, and in others 

 perhaps, in which a strong ridge stands on the median line on the 

 under surface of the lid, there occur on this ridge a number of nectar 

 glands, deeply enough sunken so that the surrounding rim makes a 

 distinct duct (8 — i6). The gland tissues are limited by a course of cells 

 with suberized radial walls. The most strikingly developed alluring glands 

 are to be found, as Macfarlane showed, distributed here and there 

 on the other leaf parts (midrib, tendril) serving to attract a wander- 

 ing population of ants which sooner or later find their way to the 

 pitcher. These glands are among the most highly developed struc- 

 turally in the plant kingdom, notably because of the deep duct {8 — 15). 



Digestive glands occur on the inner surface of the pitcher wall in 

 great numbers — as many as 6000 per cm. in A^. stenophylla, as few as 

 100 in N. gracillinia (Danser). 



Both nectar and digestive glands have the same structure. They 

 consist of a single course of deep columnar cells resting on two courses 

 of rounded cells, these lying in turn on a single course of cells having 

 their radial walls suberized, called by Macfarlane the "Hmiting" 

 layer, and being in strict continuity with the surrounding epidermis. 

 This indicates their origin which, according to Oudemans, Macfarlane 

 and Stern, is wholly epidermal, though Fenner has asserted that they 

 involve also the underlying parenchyma. His drawing is not convinc- 

 ing. As to the origin of the marginal nectar glands, these too have 

 been regarded by Macfarlane as of epidermal origin, but Stern has 

 maintained that they have two centers of origin, the deeper portion 

 of the gland being of mesophyll, and only the upper portion of epider- 

 mal origin. I have examined N. ampullaria {8 — 13), the species that 

 Stern worked with, and the evidence favors a doctrine of uniformity, 

 that they are of wholly epidermal origin. The presence of the limiting 

 layer seems to be decisive evidence. 



Anatomy of the pitcher wall. — The wall of the pitcher is thin but 

 of great strength, attributable chiefly to the thick- walled epidermis 

 both within and without, supported by the veins which have a gen- 

 erous supply of sclerenchyma. The most interesting feature of the 

 wall anatomy is the occurrence of large idioblasts with spirally thick- 

 ened walls first seen by Unger in Nepenthes (according to Man- 

 gust 1882). These are very large spindle- or rod-shaped cells with 

 clear contents, apparently merely sap, and multispiral wall thicken- 

 ings. These, when the tissues are cut or torn, are drawn out as long 

 cottony conspicuous thread. The natural expectation that these pe- 

 culiar cells are connected with the vascular tissue system is not real- 

 ized (GiLBURT 1 881) as they do not stand in any relation to, and are 

 not at any point in contact with it. 



Similar cells occur in some if not all species of Crinum (Mangin); 

 also in some orchids {Pleurothallus, Bulbophyllufn) (Trecul, through 

 Mangin); and in Salicornia (Duval-Jouve 1868). Mangin con- 

 sidered them as organs of support; and it is quite possible that they 

 contribute to the walls of the pitcher a considerable degree of mechani- 

 cal strength which they certainly display. In Dischidia the walls of the 

 pitchers have in analogous situations sclerenchyma fibers. Duval- 



