112 THE FLOWERING PLANT. 
Such water-holding receptacles are generally formed by rosettes 
of leaves, but sometimes by connate leaves, as in the teasel, 
where the cups thus constituted also digest insects that tumble 
into them. It is superfluous to remark that aquatic plants are 
protected from creeping land insects by the water surrounding 
them. 
(d.) Sticky excretions may also keep off insects. Slippery wax 
(cf. p. 41) sometimes serves this purpose, but most commonly 
sticky substances, excreted by the general surface of the epi- 
dermis or by glandular hairs, play this part. The seat of the 
secretion may be foliage leaf, stem, bract, or part of the flower. 
The butterwort, for instance, a small plant not uncommon in the 
marshy parts of mountainous districts, possesses a basal rosette 
of simple leaves, slippery from the presence of a secretion. From 
the centre of the rosette rise several scapes terminated by flowers 
something like small violets. The excretion, to the feel of which 
the plant owes its name, is poured out from innumerable mush- 
room-shaped glandular hairs. As in teasel, two purposes are 
served ; for not only are the flowers protected, but the excretion 
can digest small insects, and the edges of the leaf are sensitive, 
curling over such insects and holding them fast. Butterwort, 
therefore, is an ‘“insectivorous”’ plant, and, in fact. is closely 
related to the bladderwort, previously described (p. 62). Again, 
gooseberry has glandular hairs on the outside of the cup- 
shaped receptacle, and plumbago upon the calyx. A very in- 
teresting example is found in Polygonum amphibium, a plant 
which grows with its lower part in ditches. When there is 
plenty of water, the stem is glabrous, but it develops glandular 
hairs if the water dries up. ‘These disappear again when enough 
moisture collects to surround the base of the plant. 
(e.) Hair structures proper and thin hair-like outgrowths of the 
corolla, &c., are often arranged so as to prevent unsuitable insects 
from reaching the nectar. Instances of this kind are so numerous 
that only a few can be mentioned. A ‘“weel” of hairs (ze. a 
circlet of straight flexible hairs with ends slanting mwards) is 
often found within the tube of a gamopetalous corolla, as in dead 
nettle, verbena, and speedwell. In passion-flower the whole 
corona is split up into narrow threads. The way to the nectar 
may also be blocked by tangled masses of hairs growing on 
various parts of the flower. 
(7.) It frequently happens that foliage leaves, peduncles, bracts, 
or else parts of the flower are so shaped or arranged as to hinder 
the access of small insects. Opposite leaves (more rarely stipules 
or scattered leaves) often form a kind of collar, over which in- 
sects cannot climb from below. Thisis the case in many gentians. 
