THE LEAF 87 



a small fly touches the viscid globule at the extremity 

 of one of these tentacles, he is at once securely held ; the 

 liquid being extraordinarily sticky, and so tenacious when 

 drawn out into little strings that considerable motion may 

 be imparted to the whole leaf through a single filament 

 before it is broken. In its efforts to free itself, the fly is 

 likely to strike neighboring tentacles with its legs and 

 wings. All the tentacles touched begin almost at once to 

 bend inward, toward the center of the leaf. The fly is, in 

 fact, finally deposited on the shorter tentacles of the blade. 

 Then from all sides the tentacles converge toward the cap- 

 tured insect, and their glands pour upon it secretions of 

 digestive fluid, which now begins to flow, resembling the 

 digestive secretions of the animal stomach. The soft parts 

 of the insect are dissolved and the products of digestion 

 absorbed by the glands. Subsequently the tentacles re- 

 expand, and the secretions dry up, so that the remains of 

 the insect may be blown away or shaken off. The secre- 

 tions appear again after a time, in readiness for new prey. 



152. Bending of the tentacles was distinctly observed 

 by Darwin ten seconds after excitation. The closing 

 together of the tentacles takes from one to four or five 

 hours. The tentacles expand again in from one to seven 

 days, according to the nature of the exciting object. 



153. Pitcher Plants. Pitcher Plants, of the type repre- 

 sented by the genus Sarracenia, are also low bog plants. 

 Their general habit, and the shape of their leaves the 

 upward-curving tube, the wing on one side, and the 

 rounded, more or less arching hood at the apex, are seen 

 in the accompanying illustration (Fig. 77). In some 

 species the hood quite overarches the mouth of the pitcher. 

 Its surface and that of the throat of the pitcher are set 

 with stiff downward-pointing bristles. The tube is habitu- 

 ally half filled with water, in which the fragments of 

 insects, in all stages of decomposition, may be found in 

 considerable quantities. In most species these insects 

 have been lured by secretions of honey to the rim of the 

 pitcher ; and then slipping on the extraordinarily smooth 



