150 PLANTS WHICH EXHIBIT MOVEMENTS IN THE CAPTURE OF PREY. 
sensitive part of the leaf was subjected to prolonged or only momentary contact, 
and also upon the nature of the body touching it, whether inorganic or organic, 
non-nitrogenous or nitrogenous. When rapidly touched or stroked, the leaf folds 
together, but only remains closed for a short time. The lobes soon begin to re- 
open, and can be stimulated afresh immediately and caused to shut again. This 
is also the case when the disturbance was due to the impact of a grain of sand or 
any other inorganic body, and likewise when the stimulus proceeded from an 
organie but non-nitrogenous object. But if, on the other hand, the body upon the 
upper surface of the lamina was nitrogenous and the contact not too hasty, the 
two lobes of the leaf remain closed over the object for a longer period. They also 
Fig. 28.—Capturing apparatus of the leaves of Aldrovandia and Venus's Fly-trap. 
1 Expanded leaf of a Venus’s Fly-trap. 2 Section of a closed leaf. % One of the sensitive bristles on the surface of the leaf. 
4 Expanded leaf of Aldrovandia. 5 Section of a closed leaf. © Glands on the surface of leaf of Aldrovandia. 17 Gland 
from the wall of a Sarracenia pitcher. 
become flat and even again, and are pressed together so tightly that intervening 
bodies, if soft, are squeezed and crushed to pieces. In addition, the glands, dry 
till then, begin to secrete a slimy, colourless, highly acid juice; and this is true 
even of those glands which are not at all in contact with the nitrogenous bodies 
inclosed. The secretion flows so copiously that it can be seen in the form of drops 
if the shut lobes be forcibly separated. It covers the imprisoned body and gradu- 
ally dissolves the albuminous compounds therein contained. Afterwards, the 
secretion and the matter dissolved in it are re-absorbed by the same glands as 
previously discharged the acid liquid, containing pepsin, in response to the stimulus; 
and when the trap reopens, the glands are dry. The soluble part of the prey has 
now vanished: the six little spinous processes, which were bent in the closed leaf 
like the blades of a pocket-knife and lay pressed down upon the surface, stand up; 
and the leaf is once more equipped for making fresh captures. 
The time requisite for the digestion of a nitrogenous body resting upon the 
surface of a leaf varies according to the size of the body. The leaf usually remains 
closed for from eight to fourteen days, but often even for twenty days. Although 
