Francis E. Lloyd —66— Carnivorous Plants 



JouvE thought them to be organs of aeration, and that they were al- 

 ways in contact with sub-stomatal cavities, which is surely not the 

 case. I have satisfied myself that they are quite independent of all 

 other cells than those of the parenchyma in which they lie. They 

 occur elsewhere than in the pitchers. It is probable that they are more 

 properly to be regarded as water-reservoirs (Kny and Zimmermann 



1885). 



The vascular system. — The course of the vascular strands is such as 

 to indicate that the pitcher is produced by the expansion chiefly of the 

 abaxial moiety of the leaf, and this is also indicated by the mutual 

 approximation of the wings along the edges of the ventral surface (Mac- 

 farlane). The finer endings of the vascular tissue often but not 

 always (Macfarlane) abut on the under side of the surface 

 glands found on the interior surface of the pitcher and of the lid. The 

 fact that unopened pitchers which have been removed from the plant 

 soon lose their juice (invariably found in young pitchers before open- 

 ing) observed by de Zeeuw (1934) seems to be related to this fact. 



Surface anatomy. — By this we mean the anatomy of the epidermis, 

 that of the interior surface of the pitcher being of primary interest to 

 us. Examination of the interior of the pitcher {4 — 6) will show that, 

 with some exceptions (A^. ampullaria, hicalcarata, ventricosa, inermis) 

 there is a broad zone, beginning just beneath the rim, having a glau- 

 cous, opalescent appearance caused by an ample waxy secretion with 

 a pebbly surface. The epidermal cells here are simply polygonal with 

 the exception of a large number of slightly projecting lunate ones, so 

 placed that their concave edges are turned downwards {8 — 5). They 

 have the appearance, at once perceived, of half stomata, each in itself 

 looking like a guard cell. Oudemans (1864) thought them to be wax- 

 secreting glands. WuNSCHMANN would have none of this (1872) and 

 pronounced them to be squat hairs, broader than long. Dickson 

 (1883) was the first to arrive at the correct interpretation: "I have 

 here to note that each crescentic ledge consists of a semilunar cell 

 which overlaps a lower and smaller one. Occasionally these two cells 

 puzzlingly resemble deformed stomata," he wrote. His sometime 

 associate Macfarlane confirmed this, as did Haberlandt, independ- 

 ently, and later Bobisut (1910) showed that they are completely non- 

 functional stomata, having no pore, though Macfarlane had thought 

 otherwise. Macfarlane thought, too, that they exude water; and 

 Goebel that they might serve for gas exchange (1891), neither of 

 which can be true in the absence of a pore. I (19336) have confirmed 

 Bobisut's observations. The lunate cell is one guard cell, projecting 

 somewhat above the general level of the surface, hiding beneath itself 

 the second guard cell {8 — 6) , the whole having been rotated on the 

 longer axis. The whole waxy zone is a "conductive" (Hooker) or 

 slippery surface (Gleitzone, Goebel) on which insects such as ants 

 can find no foothold. 



It is interesting to note in this connection that Macbrlde, in 181 7, 

 made the suggestion that the inabiUty of insects to cling to the surface 

 of the pitcher of Sarracenia adunca might be due to the presence of 

 an impalpable powder, or to the breaking away of fine hairs. To this 

 question in relation to Nepenthes Knoll (1914) has directed some 

 painstaking experimentation. 



