Francis E. Lloyd — 126 — Carnivorous Plants 



Other glandular trichomes occur in D. gigantea (seen by Darwin) and 

 probably in other species. These are stalked, bear an oval gland, and 

 look superficially like the tentacles, but do not have their elaborate 

 differentiation. They are to be found scattered on the petioles and 

 stems; on the latter they are quite numerous. I failed to observe any 

 secretion. Though the gland is covered with cuticle, they absorb dye 

 readily. Their structure is indicated in i§ — i6. In origin they are 

 epidermal, but in the base there is a small involvement of parenchyma 

 as it is rather broad, the stalk tapering upward into a uniseriate por- 

 tion just beneath the gland. What function these can serve, if any, is 

 not known. Small flies have been observed sticking to them. 



Function of sessile glands. — Darwin observed that aggregation 

 takes place in the sessile glands during the digestion of prey, and 

 thought therefore that they are concerned in the absorption of sub- 

 stances derived therefrom, "but this cannot be the case with the pa- 

 pillae on the backs of the leaves or on the petiole." It is not clear if 

 he meant this merely because of unfavorable position. But Fenner 

 held that the sessile glands of the concave leaf surface are alone capable 

 of absorption, pointing out that those of the dorsal surface are small, 

 and usually lose the capital cells. The active glands display cytoplas- 

 mic changes (Darwin's aggregation evidently) during the absorption 

 of nutriment. Because nuclear changes also intervene, Rosenberg 

 aligned himself with these authors. To all this Konopka opposes a 

 contrary opinion. Nuclear changes such as Rosenberg observed are 

 also to be seen in other glands, certainly not concerned in the absorp- 

 tion of substances; and the "middle layer" (endodermis) also is to be 

 found in nectaries, hydathodes, etc. He believes the sessile glands to 

 be hydathodes. They never, he continues, show such far-reaching 

 changes in nuclear behavior as do the tentacle cells, and there never 

 occur the " Digestionsballen " which he found in tentacle gland cells. 

 Nor have the glands any connection with the vascular tissues; they 

 develop much earlier than the tentacles, and occur on both leaf faces. 

 These points argue that the sessile glands are not absorptive. There 

 is, Konopka believes, much greater probabihty that they serve the 

 purpose of water secretion. In support of this view he cites as facts 

 (a) the "not small" vascular system of the roots; (b) the rich supply 

 of root hairs; (c) the wetness of the substrate; (d) the active passage 

 of water through the plant and (e) the high relative humidity of the 

 habitat, tending to reduce transpiration. And Schmid, he says, had 

 found that there is only a slow transfer of water to the tentacle glands 

 following the experimental removal of the mucilage drop, while on the 

 capture of prey there is an extraordinary increase of fluid supplied 

 from the leaf during the digestion of prey (as Darwin and others have 

 observed), all speaking for a process of guttation. Admitting the 

 above as facts (though Schmid 's results seem to question some of 

 them) Konopka arrives at an interesting interpretation of the whole 

 situation: the sessile glands draw off water from the leaf, supplying it 

 for the process of digestion and thus at the same time exert suction on 

 the tentacles, thus increasing absorption by them. These glands, he 

 says, may be roughly compared with the animal kidney which with- 

 draws water from the body thus making room for more to be absorbed. 



