10 DROSERA ROTUNDIFOLIA. [Cbap. I. 



been carried by this movement to the centre, be not very 

 small, or if it contains soluble nitrogenous matter, it acts on 

 the central glands ; and these transmit a motor impulse to the 

 exterior tentacles, causing them to bend inwards. 



Not only the tentacles, but the blade of the leaf often, 

 but by no means always, becomes much incurved, when any 



Fig. 6. 



(Drosera rotundifolia.) 



Diagram showing one of the exterior tentacles closely inflected ; the two 



adjoining ones in their ordinary position. 



strongly exciting substance or fluid is placed on the disc. 

 Drops of milk and of a solution of nitrate of ammonia or soda 

 are particularly apt to produce this effect. The blade is thus 

 converted into a little cup. The manner in which it bends 

 varies greatly. Sometimes the apex alone, sometimes one 

 side, and sometimes both sides, become incurved. For in- 

 stance, I placed bits of hard-boiled egg on three leaves; one 

 had the apex bent towards the base; the second had both dis- 

 tal margins much incurved, so that it became almost tri- 

 angular in outline, and this perhaps is the commonest case; 

 whilst the third blade was not at all affected, though the ten- 

 tacles were as closely inflected as in the two previous cases. 

 The whole blade also generally rises or bends upwards, and 

 thus forms a smaller angle with the footstalk than it did be- 

 fore. This appears at first sight a distinct kind of movement, 

 but it results from the incurvation of that part of the margin 

 which is attached to the footstalk, causing the blade, as a 

 whole, to curve or move upwards. 



