INSECTIVOROUS AND CLIMBING PLANTS. 311 



the presence of animal or other soluble azotized mat« 

 ter, even in quantities so minute as to rival the spec- 

 troscope — that most exquisite instrument of modern 

 research — in delicacy ; and, finally, they establish the 

 fact of a true digestion, in all essential respects similar 

 to that of the stomach of animals. 



First as to sensitiveness and movement. Sensi- 

 tiveness is manifested b} 7 movement or change of form 

 in response to an external impression. The sensitive- 

 ness in the sundew is all in the gland which surmounts 

 the tentacle. To incite movement or other action, it 

 is necessary that the gland itself should be reached. 

 Anything laid on the surface of the viscid drop, the 

 spherule of clear, glairy liquid which it secretes, pro- 

 duces no effect unless it sinks through to the gland ; 

 or unless the substance is soluble and reaches it in 

 solution, which, in the case of certain substances, has 

 the same effect. But the glands themselves do not 

 move, nor does any neighboring portion of the ten- 

 tacle. The outer and longer tentacles bend inward 

 (toward the centre of the leaf) promptly, when the 

 gland is irritated or stimulated, sweeping through an 

 arc of 180° or less, or more — the quickness and the 

 extent of the inflection depending, in equally vigorous 

 leaves, upon the amount of irritation or stimulation, 

 and also upon its kind. A tentacle with a particle of 

 raw meat on its gland sometimes visibly begins to 

 bend in ten seconds, becomes strongly incurved in five 

 minutes, and its tip reaches the centre of the leaf in 

 half an hour ; but this is a case of extreme rapidity. 

 A particle of cinder, chalk, or sand, will also incite 

 the bending, if actually brought in contact with the 



