Chapter VI — 91 — Genlisea 



in form, and trap leaves, all arising densely crowded and without trace- 

 able order, from a slender rhizome, very much as the leaves and stolons 

 arise from the radially symmetrical corm-like stem of the seedling of 

 Utricularia. There are no axillary buds, again as in Utricularia, 

 but the rhizome produces a few branches toward the apex, which is 

 the widest part. The trap leaves arise like the stolons of Utricularia 

 and at first look like them. At first cyHndrical with a tapering grow- 

 ing point, they grow out for some distance (i cm. or more or less) be- 

 fore any further differentation takes place. In structure this portion 

 consists of epidermis inclosing a very extensive intercellular air space 

 of lysigenous origin. In the dorsal sector lies a cord of relatively few 

 parenchyma cells surrounding the vascular tissue, again quite hke a 

 Utricularia stolon. This portion may be called the foot stalk, but not 

 petiole since this leaf region is produced by intercalary extension be- 

 tween the leaf base and the apex, while, as Goebel pointed out, the 

 base at the foot stalk is the oldest portion of the trap leaf, which ex- 

 tends solely by apical growth. At length the end of the footstalk be- 

 gins to widen and an invagination takes place just behind the tip and 

 on the ventral (upper) side. The basal portion of the invagination be- 

 comes a subspherical hollow bulb. The neck of this bulb extends for 

 some distance to form a tube, which toward the mouth gradually 

 widens to right and left, so that the opening becomes a transverse slit, 

 with the lips dorsal and ventral, the latter being shorter, and the for- 

 mer being more or less arched over the opening. The angles of the 

 mouth develop into two long arms with circinate apices, the slit being 

 on the outer curve of the crook (// — 3, 4, 7). During elongation and 

 resulting from rotatory growth, the arms become twisted, the one on 

 the right, clockwise, the other counter clockwise {11 — 8, 10). In 

 consequence one lip of the mouth of the arm, which extends through- 

 out its length, becomes longer than the other, so that, if an arm be 

 laid open it takes the form of a spiral ribbon {11 — 9). The arms may 

 be likened to two ribbons folded longitudinally and twisted on the long 

 axis so that the two edges form spirals roughly parallel to each other. 

 One edge becomes the inner, and in the plant is the shorter. In the 

 actual trap, the two edges are anchored to each other at short inter- 

 vals. This is accomplished by large marginal cells, cystid-like in ap- 

 pearance, which during growth become pressed into, and adherent to, 

 the tissue of the apposed edge. These large cells we may with Goebel 

 term prop-cells. They were first described by Goebel (1891) but not 



quite correctly. He wrote " the funnel shaped entrances are 



formed by the occurrence at certain distances apart of two large clear 

 cells which He the one upon the other, and which may be called prop- 

 cells. They are merely the end cells of the rows of trapping hairs in 

 which, however, the hair itself is merely one-celled, while the cell be- 

 neath is swollen to a giant size." By making a paper model it will be 

 seen, continues Goebel, "that in order that the two prop-cells shall 

 really meet each other it is necessary that the shorter edge of the arm 



shall be bent outwardly. One can see the two prop-cells " 



This passage is quoted to indicate that Goebel thought that there is 

 a row of prop-cells along each margin of the arm entrance, and that 

 during development these meet and adhere in pairs, the one prop-cell 



