Pitcher-plant or Side-saddle Flower (Sarracenia, Fig. 174) of our bogs.
These pitchers are generally half full of water, in which flies and
other insects are drowned, often in such numbers as to make a rich
manure for the plant. More curious are some of the southern species of
Sarracenia, which seem to be specially adapted to the capture and
destruction of flies and other insects.

[Illustration: Fig. 174. Leaf of Sarracenia purpurea, entire, and
another with the upper part cut off.]

172. The leaf of Nepenthes (Fig. 175) combines three structures and
uses. The expanded part below is foliage: this tapers into a tendril for
climbing; and this bears a pitcher with a lid. Insects are caught, and
perhaps digested, in the pitcher.

[Illustration: Fig. 175. Leaf of Nepenthes; foliage, tendril, and
pitcher combined.]

[Illustration: Fig. 176. Leaves of Dionaea; the trap in one of them open,
in the others closed.]

173. =Leaves as Fly-traps.= Insects are caught in another way, and more
expertly, by the most extraordinary of all the plants of this country,
the Dionaea or Venus's Fly-trap, which grows in the sandy bogs around
Wilmington, North Carolina. Here (Fig. 176) each leaf bears at its
summit an appendage which opens and shuts, in shape something like a
steel-trap, and operating much like one. For when open, no sooner does a
fly alight on its surface, and brush against any one of the two or three
bristles that grow there, than the trap suddenly closes, capturing the
intruder. If the fly escapes, the trap soon slowly opens, and is ready
for another capture. When retained, the insect is after a time moistened
by a secretion from minute glands of the inner surface, and is digested.
In the various species of Drosera or Sundew, insects are caught by
sticking fast to very viscid glands at the tip of strong bristles, aided
by adjacent gland-tipped bristles which bend slowly toward the captive.
The use of such adaptations and operations may be explained in another
place.

Sec. 3. STIPULES.

174. A leaf complete in its parts consists of blade, leaf-stalk or
petiole, and a pair of stipules. But most leaves have either fugacious
or minute stipules or none at all; many have no petiole (the blade being
_sessile_ or stalkless); some have no clear distinction of blade and
petiole; and many of these, such as those of the Onion and all phyllodia
(166), consist of petiole only.

175. The base of the petiole is apt to be broadened