296 THE STRUCTURES OF PITCHER PLANTS. 
Xanthoptera semicrocea and Sarcophaga sarracenie, said by Professor 
Riley to be the only two insects which can escape from the pitchers of 
the Sarracenia, to overcome this formidable chevaua de frise. In the 
case of the latter insect it is probable that the grub is deposited in the 
pitcher by the mother before the special armature of the first zone is 
developed. This development afterwards leads to the peculiar method 
of escape of the mature grub in a way serviceable to the plant in which 
it has fed. Sparsely scattered over this surface are multifid buds, 
raised above the epithelial level for the greater part of their bulk, but 
slightly dipping below it, being therefore transitions from the 
multifid bud to the ostiole. I have failed to find anything which I could 
regard as nectaries on this surface. It ends quite abruptly in a line of 
crescentic markings, armed with stunted setz, and when wetted it does 
not throw off water. (Fig. 9.) The second zone presents to the naked 
eye a remarkable bald appearance, and when wetted it throws off the 
water, a circumstance which seems to be due to a peculiar arrangement 
of the epithelium. Hach cell is produced into a mammillary process, 
(Fig. 9,) pointing downwards, and is marked by a number of flutings, 
like the back of a pecten shell, these flutings converging towards the 
apex of the process. The process of each cell overlaps the upper margin 
of the cell immediately below it, and in this way a subsidiary barrier is 
formed which must prevent the egress of insects small enough to ¢reep 
between the large sete of the first zone. On this surface the inter- 
cellular spaces are evidently canalicular, and multifid buds abound, but 
they are covered by the altered epithelium. Whether this covering 
means that they are only hidden by the peculiar development of the 
epithelium, or are really embedded, I am unable to say. This zone is 
about six millimetres wide, and ends as abruptly as it begins. I have 
failed to obtain any evidence of secretion from this surface, and there- 
fore I regard its glandular structure as purely absorbent. Stomata are 
of very occasional occurrence on this surface. In the third zone the 
epithelium is of the sinuous pattern, with well marked intercellular 
canals and very abundant included glands. These bodies are 
entirely covered by the epithelium, the divisions of their proto- 
plasm appearing, however, very close under the surface. They are 
about :065 of a millimetre. There are no stomata on this surface. The 
transition from the third to the fourth and most extensive zone is rapid, 
but not quite sudden, and consists in an alteration of the cells of the 
epithelium from the sinuous shape into irregular polygons. The sub- 
epithelial cells are, however, of the sinuous shape, a fact which may 
account for the view expressed by Dr. Hooker, that this fourth zone has 
no cuticle. There are no stomata to be found in this zone, and no 
subepithelial glands, the place of the latter seeming to be taken by the 
tubular trichomes already described. These trichomes are not nearly so 
stiff and strong as the set on the first zone, and the surface on which 
they are situated is peculiarly retentive of water, the innumerable hairs 
taking it up between them like a sponge. I have not seen spiral vessels 
in the tissue of Sarracenia purpurca. All my efforts to discover the 
presence of any ferment having digestive properties in the fluid taken 
