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 

 organic 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. 23. — Capturing apparatus of the leaves of Aldrovandia and Venus's Fly-trap. 



1 Expanded leaf of a Venus's Fly-trap. - Section of a closed leaf. 3 One of the sensitive bristles on the surface of the leaf. 

 * Expanded leaf of Aldrovandia. « Section of a closed leaf. 6 Glands on the surface of leaf of Aldrovandia. ' 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 foi - cibly 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 sis 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 



