30 DROSERA ROTUNDIFOLIA. Crap. IL 
prominence, often came to touch, sooner or later, the 
gland. 
In the foregoing and following cases, it is probable 
that the vibrations, to which the furniture in every 
room is continually liable, aids in bringing the par- 
ticles into contact with the glands. But as it was 
sometimes difficult, owing to the refraction of the secre- 
tion, to feel sure whether the particles were in contact, 
I tried the following experiment. Unusually minute 
particles of glass, hair, and cork, were gently placed or 
the drops round several glands, and very few of the 
tentacles moved. Those which were not affected were 
left for about half an hour, and the particles were 
then disturbed or tilted up several times with a fine 
needle under the microscope, the glands not being 
touched. And now in +h. course of a few minutes 
almost all the hitherto motionless tentacles began to 
move; and this, no doubt, was caused by one end or 
some prominence of the particles having come into 
contact with the surface of the glands. But as the 
particles were unusually minute, the movement was 
small. 
Lastly, some dark blue glass pounded into fine 
splinters was used, in order that the points of the par- 
ticles might be better distinguished when immersed in 
the secretion ; and thirteen such particles were placed 
in contact with the depending and therefore thicker 
part of the drops round so many glands. Five of the 
tentacles began moving after an interval of a few 
minutes, and in these cases I clearly saw that the par- 
ticles touched the lower surface of the gland. A sixth 
tentacle moved after 1 hr. 45 m., and the particle 
was now in contact with the gland, which was not the 
case at first. So it was with the seventh tentacle, but 
its movement did not begin until 3 hrs. 45 m. had 
