198 
THE DICTIONARY 
OF GARDENING, 
Fic. 207. DION®A MUSCIPULA. 
CARNIVOROUS PLANTS. This term is usually 
applied to genera like Drosera, Pingwicula, Nepenthes, 
Dionzxa, and Utricularia, which are thought by some to 
possess the power of absorbing nitrogenous substances 
through their leaves, and digesting them within their 
tissues. Several of the best known are British plants— 
Fia, 
208, DROSERA ROTUNDIFOLIA (natural size). 
Carnivorous Plants—continued. 
Drosera rotundifolia and D. intermedia for instance. The 
most interesting of all, however, is Dionza muscipula (Fig. 
207), or Venus’ Fly-trap. 
Others regard these plants as insect-catching rather than 
insect-eating, their contention being that the plants have 
no power to cast away the captured prey, which gradually 
decays upon the leaf. In fact, it has been observed that 
when the creature trapped proves to be a rather large 
insect, or perhaps a spider, the decomposition that follows 
after death frequently causes the destruction of the leaf. 
As Drosera rotundifovia 
will serve as well as any 
to illustrate the functions 
of these interesting plants, it i 
has been selected here (Fig. q@ 
208). The leafis the interest- » “i= _ 
ing part of the plant. It bears © 
on its upper surface a large 
number of filaments, or 
tentacles, as they are usually 
called. Some large leaves 
have as many as 250, but 
usually there are not more 
than 100. Those in the 
marginal row, which are 
often jin. in length, spread 
out in the plane of the 
surface of the leaf; the 
members of the next row 
are shorter and rather more 
erect, and so on, till those 
in the central part of the 
leaf are very short and quite 
erect (see Fig. 209). There 
are a very few long tentacles 
on the upper part of the 
leaf-stalk. At the extremity = 
of each tentacle is a gland surrounded by a globule of 
a clear fluid of the consistency of gum. It is not certain 
whether the tentacles are hairs modified to perform a 
special duty, or prolongations of the leaf itself; but at 
any rate the framework of the 
leaf enters into them, as will 
be seen in the much-magnified 
drawing of one of the glands 
(see Fig. 210). The central spiral 
threads are in connection with 
the fibro-vascular system of the 
leaf; outside of them are two or 
three layers of simple cells con- 
taining a purplish fluid, which 
undergoes a change when the 
gland is irritated. The pale 
green leaf, with its crimson ten- 
tacles, surmounted with glistening 
drops of liquid, looks very beau- 
tiful in the sunshine, and well 
earns for the plant the common 
name of Sundew. The plant is 
at its best in July and August, 
and flowers in the latter month. 
Suppose a tiny fly to alight 
upon the central part of a 
leaf, it will be held there by 
the sticky substance surround- 
ing the glands on the tentacles. The glands at once 
begin secreting a watery fluid closely resembling pepsin 
in its properties, and which, like it, dissolves organic 
food. At the same time an impulse travels along the 
fibro-vascular system to the outer tentacles. These in 
the course of an hour gradually turn over, the nearer ones 
LEAF OF DROSERA 
ROTUNDIFOLIA 
(magnified two diameters). 
Fie. 209. 
Fia. 210. GLAND OF DROSERA 
ROTUNDIFOLIA 
(much magnified). 
first and the remoter ones later, on to the insect, and 
there pour out the same fluid. When, after a few days, 
