Francis E. Lloyd — 118 — Carnivorous Plants 



in the volute a large number of the tentacles are exposed and cannot 

 receive protection from the overlying turn of the volute. I have ob- 

 served this and can confirm Goebel on the point. On the other hand, 

 GoEBEL proposes a causal explanation as follows. The production of 

 a great extension of surface by the growth of tentacles can act to in- 

 hibit the growth rate of that surface, and thus permit the more rapid 

 growth of the other face of the leaf, the lower in Drosera, the upper 

 in Drosophyllum (Goebel, 1924). In Byhlis gigantea the leaf shows no 

 such movements. The leaf grows in a basal zone, and the filiform blade 

 extends always straight on. In this the glands are more numerous on 

 the lower surface. Here the distribution of the very numerous glands 

 either has no inhibiting effect, or has an equal effect on all sides of the 

 leaf. 



Of particular interest to us here are the leaves, which are the 

 mechanism for catching and digesting prey. These present a variety of 

 forms from a simple orbiculate bifacial leaf of small size {D. rotundi- 

 folia I cm. diam.) through linear {D. filiformis) to broad liguliform 

 tapering at both ends {D. regia). Or the blade may be once to twice 

 forked {D. binata, D. dichotoma) the petioles firm and cylindrical 

 ("rush-like" as Darwin put it). Further, the leaf may be peltate, 

 either obliquely {D. pygmaea) or centrally {D. gigantea, D. peltata, 

 D. subhirtella), sometimes with two basal lobes {D. auriculata) making 

 the leaf base angular, a condition reaching its maximum expression in 

 D. lunata (E. Asia). In the seedlings of the peltate leafed species the pri- 

 mary seedling leaves are usually non-peltate, those of D. peltata re- 

 sembling the following leaves of D. rotundifolia (Diels, Goebel). 



The leaf is conspicuous because of its glands raised on elongated 

 stalks, each bearing a drop of mucilage which is extremely viscid and 

 serves to entrap small insects. Erasmus Darwin thought that "Dro- 

 sera mucilage prevents small insects from infesting the leaves" (The 

 Botanic Garden, vol. 2, Canto i, p. 229). 



Anatomy of the leaf blade. — The epidermis is composed of straight- 

 walled cells in D. rotundifolia and D. capensis, but in D. Whittakeri 

 the lower epidermis is wavy-walled, the upper straight-walled. In 

 these species the cells have many chloroplasts, absent from the lower 

 epidermis of D. rotundifolia (Solereder). 



The internal parenchyma has no palisade, as pointed out by 

 NiTSCHKE, the whole being made up of rounded cells in rather few 

 courses, more in some species {D. Whittakeri) than in others {D. ro- 

 tundifolia). In the latter species there are, in the case examined by me, 

 3 to 5 courses of cells. The smallest are in contact with the upper 

 epidermis. Below there are much larger cells, the third course in con- 

 tact with the lower epidermis unless a fourth course occurs, when the 

 cells are somewhat smaller, but still larger than the upper course 

 cells (/J — 15). All the cells, usually including the epidermis (Solere- 

 der), contain chloroplasts. Stomata occur on both surfaces. The in- 

 tercellular spaces are large. This general structure is, as Schmid 

 (191 2) has said, rather primitive, a quality which is shared, in varying 

 degree, with insectivorous plants in general, indicating that this qual- 

 ity stands in a probable relation to carnivory. In these plants the 

 elaboration of starch and its metabolism and withdrawal are all slow 

 processes. 



