Francis E. Lloyd — 62 — Carnivorous Plants 



As to the pitcher wings, which show a wide variety of definitive 

 development, they may be considered as secondary outgrowths, like 

 those of Cephalotus or, as Goebel held, hke the keel of Sarracenia. 

 Others have held them to be leaf margins. Troll comes to the con- 

 clusion that they are the edges of the leaf base dragged out (ver- 

 schleppte), while growing themselves, by the growing petiole and leaf 

 beneath. Concerning the lid, its interpretation, before Hooker rec- 

 ognized the spur as the true apex of the pitcher leaf, was easy, as 

 being the true apex. Stern 's suggestion that it arises by a longitudinal 

 splitting of the apical meristem is untenable in view of the anatomical 

 facts. The views of Bower, Macfarlane and Goebel are also dis- 

 carded. The key to the problem, says Troll, is to be found in the 

 structure of the spur, which is unifacial, from which it follows that 

 the edges of the leaf blade at its base run together and unite (total 

 stipulation). Important here is a fact, pointed out by Heide (1910) 

 that the inner (lower) face of the lid is anatomically identical with that 

 of the interior of the pitcher, and the upper (outer) with that of the 

 outer pitcher surface. The lid cannot therefore be an "outgrowth of 

 the upper surface" as Goebel held. It should here be noted that 

 Dickson stated (and truly) that the base of the lid in primary leaves 

 (as also in other juvenile leaves) is very broad, extending "around 

 fully one half of the orifice of the pitcher" (7 — 7). Troll's view as 

 just stated is certainly supported by an examination of the venation of 

 even old adult pitchers in which the isthmus between the orifice and 

 the lid is very narrow. A macerated preparation of A^. formosa demon- 

 strates this, by which it is seen that, as already indicated in discussing 

 primary leaves, the venation is but that of a totally stipulate leaf 

 blade, sharply constricted below the apex. The apical portion, the lid, 

 may in adult leaves be supplied with a midvein which is secondary 

 since in primary leaves such a midvein does not exist. And when pres- 

 ent, as it is in adult leaves, it is evidently smaller and is dominated 

 by the lateral veins. 



A novel interpretation of the rim, lid and spur has been advanced 

 by Mrs. Arber (1941). In doing this she rejects all earlier views, that 

 of Troll included, which hold that the lid is a transversal pinna. If 

 Troll is right, she says, the veins of the fid should have their wood 

 upwards, not downwards. She questions also the statement of Troll 

 that the spur is unifacial, though admitting that the veins of the spur 

 "tend toward a radial arrangement." Had Troll selected A'^. intermedia 

 and/or A^. hicalcarata for study, his evidence would have been still 

 more convincing. Having disposed of the spur as the leaf apex, Mrs. 

 Arber argues that "both the lid and the median point are merely 

 localized expressions of collar-forming activity, which is responsible for 

 the double curve-over of the aperture edge .... the lid, which is 

 turned down in youth, corresponding to the inner curve-over, and the 

 median point to the outer curve-over." 



"The relative hypertrophy of the lid and median point may be 

 correlated with the special character of the venation .... of the 

 parallel type as in other pitchers. The midrib passes directly to the 

 junction of the hd and median point, while the veins of the adaxial 

 part of the pitcher also show a strong tendency to converge upon the 



