Insectivorous Plants ( Part II). 413 
very abundant. The junction of attractive and conducting 
surfaces is very abrupt, and forms a line running round the 
interior of the hood, on a level with the pitcher-orifice. The 
conducting surface, which is a narrow zone from | to f inch in 
depth, has few or no glands. Along its upper region each 
cell is produced into an extremely short downward-growing 
point ; lower down, however, the cells gradually lengthen until 
they resemble similar cells of S. purpurea. The detentive 
surface includes the greater part of the pitcher-tube. Its 
hairs are very long, and, in striking contrast to the conducting 
surface, it is abundantly supplied with glands over its upper 
third. In no other species are there so few on the conducting, 
and so many on the upper region of the detentive surface. 
In all the species, then, an amount of sweet juice is secreted 
corresponding in quantity to the number of alluring and 
attractive glands. Sir J. Hooker suggests that it is probably 
ground-game which is led up to the pitchers, and while this 
may be true to some extent, in our greenhouses flying insects 
almost entirely are caught, and these consist in about eighteen 
cases out of twenty of bluebottle flies, with an occasional ear- 
wig, wasp, or house-fly. These alight on some part of the 
tube and gradually crawl up to the pitcher-mouth, sipping 
the honeyed juice as they go. It may be that in their native 
haunts running insects or even, as in the case already men- 
tioned of Darlingtonia , slugs form part of the prey, but that 
flying insects are as easily captured is undoubted 1 . 
If we now make a short comparative review of the six 
species it will be manifest that vS. variolaris is a central type 
from which the others radiate off. I do not necessarily mean 
by this that they have been derived from it by evolutionary 
modification, but rather, that in process of evolution the 
1 Since writing the above I have had the opportunity of examining S. purpurea 
in the New Jersey Swamps, and find that ground-game, notably ants, are largely 
caught by the pitchers. Flying insects and slugs are not uncommon, and though 
bulk for bulk they may yield a considerable food-supply for the plants, Hooker’s 
supposition appears correct for this species. In one specimen examined a large 
nest of ants had been established in three of the older and rather dry brown leaves, 
just beneath the reddish green leaves that were actively catching prey. 
