Chapter X — 125 — Drosera 



seems to indicate that whatever the function of the endodermis, it is a 

 different one from that of the secretion layer, and this I believe is as 

 far as we can go in interpretation beyond admitting that substances 

 are transmitted, but not differentially. 



KoNOPKA also questions Fenner's view about the neck cells. He 

 does violence to Fenner's definition of the neck cells by including the 

 uppermost parenchyma cells which lie somewhat (but very little) above 

 the level of the ring or circle ("Kranz") of neck cells. The neck cells, 

 as he uses the term, have membranes which resist the action of 

 concentrated sulfuric acid, and are similar in this respect to the endo- 

 dermis cells. Discarding Fenner's idea that they are especially con- 

 cerned with the transmission of water to the surface, he thinks that, 

 on the basis of his observation of the nuclear changes, which are sim- 

 ilar to those seen in the endodermal, tracheid and stalk cells, they 

 transmit absorbed materials downwardly to the stalk. This seems to 

 be a simple and natural view of the matter. But I have been unable 

 to see cuticularized walls in these cells, and Fenner says nothing of 

 this (75 — 12). Nor have others (Huie, Homes, myself) seen nuclei in 

 the xylem of the mature gland. 



We may summarize what has been said in the few preceding para- 

 graphs by emphasizing the very complex functioning of the tentacle 

 gland, that it is, as a mechanism, relatively complex as compared with 

 many other known plant glands, but that we are far from recognizing 

 specific correlations between structure and function. It would seem 

 that the complexity of function is much greater than recognizable 

 structural differentiation. 



Sessile glands. — ■ In addition to the stalked glands or tentacles 

 there are very numerous, small sessile glands, or, as Darwin called 

 them, "papillae". They were described for the European species by 

 Nitschke and others, and in detail by Fenner, who traced their 

 development. They are to be found on both leaf surfaces, on the 

 stalks of the tentacles, and elsewhere (petioles, scapes). The glands 

 project dome-shaped from the leaf surface, are little larger than the 

 stomata in area, and consist of a capital of two cells, which may be 

 rounded and compact, or more or less elongated into obliquely placed 

 cylinders. These stand on a short stalk of compressed cells in two 

 courses, each course of two cells. The basal cells have cuticularized 

 inner walls. These in turn stand on two epidermal cells (75 — -18). 

 Fenner describes also a variant of the fundamental form. It occcurs 

 on the petioles, and consists of a more or less elongated stalk with a 

 capital of about four cells. 



The origin of the sessile glands is purely epidermal (Fenner). 

 The mother cells are two short epidermal ones which by tangential 

 division give rise to a pair of capital cells, the base of which is again 

 cut off to make stalk cells. The remaining true capital cells are two 

 in number and may remain rounded, or elongate more or less into two 

 divergent short cylindrical cells, seen on the base of the tentacles and 

 on the petiole (Nitschke). In D. Whittakeri these glands are much 

 larger and more complicated in structure and consist of twelve cells, 

 eight outer surrounding a core of four inner, the whole being supported 

 on a very short biseriate stalk of longitudinally compressed cells. 



