Francis E. Lloyd — 22 — Carnivorous Plants 



verse section. The ascidium is present. Corresponding dimensional 

 changes take place in the component cells, but there is also, according 

 to MacDougal, an actual increase in the number of cells in the 

 elongated portion of the detentive region (which partakes in elonga- 

 tion with the petiole) and an actual decrease in the number of cells 

 of the conductive surfaces (zones i and 2). Thus the pitcher of Sar- 

 racenia behaves, in relation to light, as if it were a leaf blade (zones 

 I, 2 and the upper part of 3) and the rest as if it were petiolar (1903, 

 pp. 173-6). Iris, when grown in the dark, grew only slightly in excess 

 of the normal. We recall that Goebel compares the Sarracenia leaf 

 with that of Iris. 



The juvenile leaves, which are also pitcher leaves, differ in some 

 details from the mature. While they display the same zonation, the 

 characters as they have been described for the mature leaves overlap. 

 They can be described as follows: 



Zone I is the same as in the mature leaves. The margin of the flap 

 is ciliated with more or less curved blunt hairs. The epidermal cells 

 are sinuous walled, the glands present but few. Stomata are present 

 and the hairs stout and curved. 



Zone 2. The epidermis of zone i changes abruptly in that all the 

 cells become trichomatous, but very short and produce the effect of 

 imbrication, as described above. Glands are large and numerous, 

 more so towards the lower limit of the zone, where the epidermis 

 again changes. 



Zone 3. The epidermal cells are again sinuous walled but, unhke 

 the mature leaf, there are numerous trichomes. Glands are here also 

 present, but no stomata. 



Zone 4. The epidermal cells become straight, the cells isodiametric, 

 with numerous very slender hairs, and no glands, and no cuticle. 



Zone 5 has the same sort of epidermis as zone 4, but is devoid of 

 hairs. 



As we shall see, the, juvenile leaf of S. purpurea resembles in struc- 

 ture that of 5. psittacina. 



We come to the details of the glands and trichomes. The glands 

 (j — i) are all of one type (the ''Sarracenia type," Goebel, 1891). 

 Viewed as part of the general surface, each gland exposes normally 

 six cells to view, four in a rough circle and two, the cover cells (Goe- 

 bel) in the middle (2 — 15). The cover cells overlap the four bor- 

 dering cells to a greater or less extent. Those on the outer surface 

 have relatively large cover cells, which jut out further beyond the 

 general level of the surface. Those of the glands of zone 2 are rela- 

 tively much smaller. 



The outer surface glands (2 — 15, 16) are the smallest and simplest 

 in structure, derived from a single epidermal cell, according to Zip- 

 perer and to Fenner. Undoubtedly the gland is of epidermal ori- 

 gin, and the idea is not precluded that it may represent originally a 

 stomatal apparatus, the cover cells arising originally as guard cells. 

 But this is admittedly speculation. The four peripheral cells lie in 

 the general level of the surrounding epidermal cells, while the two 

 cover cells are conical and are wedged in between the peripheral cells. 

 Against the interior faces of the peripheral cells there is usually one, 



