LEAVES OF PECULIAR FORMS AND USES. 105 
How much the common American pitcher plants depend for 
nourishment on the drowned insects in the pitchers is not 
definitely known, but it is certain that some of the tropical 
species require such food.’ 
In other rather common plants, the sundews, insects are 
caught by a sticky secretion which proceeds from hairs on 
the leaves. In one of the commonest sundews the leaves 
consist of a roundish blade, borne on a moderately long 
petiole. On the inner surface and round the margin of the 
blade (Fig. 95) are borne 
a considerable number of 
short bristles, each ter- 
minating in a knob which 
is covered with a clear, 
sticky liquid. When a 
small insect touches one 
of the sticky knobs, he is 
held fast and the hairs at 
once begin to close over 
him, as shown in Fig. 
; Fic. 94. — Leaves of Sundew. (Slightly magni- 
94. Here he soon dies fied.) 
and then usually remains The one at the left has all its tentacles closed 
over captured prey; the one at the right has 
for many days, while the only half of them thus closed. 
leaf pours out a juice by 
which the soluble parts of the insect are digested. The 
liquid containing the digested portions is then absorbed by 
the leaf and contributes an important part of the nourish- 
ment of the plant, while the undigested fragments, such as 
legs, wing-cases, and so on remain on the surface of the leaf 
or may drop off after the hairs let go their hold on the 
captive insect. 
1 Where the Sarracenia is abundant it will be found interesting and profitable to 
make a careful class study of its leaves. See Geddes, Chapters in Modern Botany, 
Chapters I and II. 
