12 DROSERA EOTUNDirOLIA. Chap. I, 



placed on its gland ; and I have often seen strongly 

 pronounced inflection in under one minute. It is sur- 

 prising liow minute a particle of any substance, such 

 as a bit of thread or hair or splinter of glass, if placed 

 in actual contact with the surface of a gland, suffices 

 to cause the tentacle to bend. If the object, which has 

 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 in- 

 carved, when any strongly exciting substance or fluid 

 is placed on the disc. Droj)s 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 

 instance, I placed bits of hard-boiled egg on three 

 leaves ; one had the apex bent towards the base ; the 

 second had both distal margins much incurved, so 

 that it became almost triangular in outline, and this 

 perhaps is the commonest case ; whilst the third blade 

 was not at all affected, though the tentacles 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 before. 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. 

 • The length of time during which the tentacles as 



