144 PLANTS WHICH EXHIBIT MOVEMENTS IN THE CAPTURE OF PREY. 
species of Drosera, is the presence of the delicate wine-red filaments, clavate 
at their free ends and each supporting a glistening droplet of fluid, which stand 
out from the leaves, and whose function is essentially the same as that of the 
glands, stalked and sessile, on the leaf of Pingwieula. These filaments only 
proceed from the upper surface and margin of the sun-dew leaf. The under surface 
is smooth and hairless, and in many species, including the Drosera rotundifolia 
depicted on the plate, it rests upon the damp mossy ground. In this particular, 
and also in the circumstance that all the leaves of each individual are adpressed to 
the ground and grouped in a rosette or radially around the central slender flower- 
ing-stem, there exists a very obvious analogy between Drosera, and not Pingwieula 
alone, but many other carnivorous plants, such as Sarracenia, Heliamphora, Cepha- 
lotus, and Dionca, the fly-trap presently to be described. 
The filaments or tentacles projecting from the upper surface and margin of the 
leaf look like pins inserted in a flat cushion and are of unequal size. Those which 
stand up perpendicularly from the middle are the shortest, and those which radiate 
from the outermost edge are the longest (see fig. 26*). Between these extremes 
are intermediate lengths gradually leading from the one to the other. There are 
on a leaf, in round numbers, about two hundred of these tentacles. The clavate 
head at the free extremity of each tentacle is really a gland. It secrets a clear, 
thick, sticky matter which is readily drawn out into threads, and which shines 
and glitters in the sunlight like a drop of dew, whence the plant has derived 
its name of sun-dew. Shocks occasioned by wind or the dropping of rain do not 
excite any kind of movement in the tentacles. If grains of sand are blown upon 
them by the wind, or if little bits of glass, coal, gum, or sugar, or minute quantities 
of paste, wine, tea, or any other non-nitrogenous substance are brought by artificial 
means into contact with the enlarged extremities of the tentacles, the exudation of 
liquid at the places in question is augmented, and the secretion also becomes acid, 
but there is no elimination of pepsin, and no change of importance ensues in the 
direction of the tentacles, or the attitude of the leaf-margin. But the moment 
a small insect, mistaking the glittering drops on the tentacles for honey as it 
flies by, alights on the leaf and so touches the glands, or upon the artificial 
placing of particles of nitrogenous organic matter, such as flesh or albumen, on the 
tentacle-heads, there ensues, as in the case of Pinguicula, an increase in the dis- 
charge of acid juice, as well as the addition of a ferment to its composition. The 
action of this ferment on albuminous compounds is entirely similar to that of 
pepsin, and we may even go so far as to speak of it as pepsin. 
The insects that fly on to the leaves and are caught by the sticky juice try to 
disencumber themselves by stroking the viscous matter off with their legs, but they 
only besmear themselves still more, and are soon plastered all over the body, and 
have their movements greatly impeded by the secretion. Their efforts to save 
themselves soon cease, the orifices of their respiratory organs are covered with the 
juice and choked, and after a brief interval they die from suffocation. All these 
phenomena correspond, in the main, to those occasioned by identical causes in the 
