12 DROSERA ROTUNDIFOLIA. Cuap. L 
placed on its gland; and I have often seeu strongly 
pronounced inflection in under one minute. It is sur- 
prising how 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- 
curved, when any 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 
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 
