36 DROSERA ROTUNDIFOLIA. Cuap. IL. 
though the secretion is so viscid that it can be re- 
moved with difficulty merely by waving the leaves in 
water. If the falling drops of water are small, they 
adhere to the secretion, the weight of which must be 
increased in a much greater degree, as before re- 
marked, than by the addition of minute particles of 
solid matter ; yet the drops never cause the tentacles 
to become inflected. It would obviously have been a 
great evil to the plant (as in the case of occasional 
touches) if the tentacles were excited to bend by 
every shower of rain; but this evil has been avoided 
by the glands either having become through habit 
insensible to the blows and prolonged pressure of 
drops of water, or to their having been originally 
rendered sensitive solely to the contact of solid bodies. 
We shall hereafter see that the filaments on the leaves 
of Dionza are likewise insensible to the impact of 
fluids, though exquisitely sensitive to momentary 
touches from any solid body. 
When the pedicel of a tentacle is cut off by a 
sharp pair of scissors quite close beneath the gland, 
the tentacle generally becomes inflected. I tried this 
experiment repeatedly, as I was much surprised at the 
fact, for all other parts of the pedicels are insensible to 
any stimulus. These headless tentacles after a time 
re-expand; but I shall return to this subject. On the 
other hand, I .occasionally succeeded in crushing a 
gland between a pair of pincers, but this caused no 
inflection. In this latter case the tentacles seem 
paralysed, as likewise follows from the action of too 
strong solutions of certain salts, and by too great 
heat, whilst weaker solutions of the same salts and a 
more gentle heat cause movement. We shall also see 
in future chapters that various other fluids, some 
