198 I'he Philippine Journal of Science \m 
r 
tion, the spreading was in some cases slightly retarded; but 
the lips resumed their original position and appeared to be as 
sensitive as if no pollen had been applied. Small quantities 
of quartz flour likewise had little or no effect on the movement 
or sensitiveness of the lips. These results seemed to show that 
those obtained with the Martynia pollen could not have been 
due to its weight acting as a mechanical stimulus but rather 
that it produced a chemical stimulation. 
When the lips were completely covered with fine quartz flour 
and then made to close together, they only opened slightly, after 
which they again closed, as in the case of the Martynia pollen. 
At the same time as large a quantity of quartz sand as could 
be placed on the lips did not seem to retard their spreading 
or to have any effect in rendering them insensitive. The expla- 
nation of these phenomena is not at all clear. If the weight 
of the quartz flour could have been effective in holding the lips 
together the same thing should have been true of the sand. 
It may be noted here that Brown and Sharp ' have found that 
continuous pressure was not effective in producing stimulation 
in the case of Dionaea. The results moreover could hardly have 
been due to any phenomena connected with growth. The best 
explanation would seem to be that there was a reduction in 
the turgor of the cells of the upper surface which was accom- 
panied by an escape of water such as results from the stimula- 
tion of the pulvini of Mimosa and the stamens of the Cynareae 
and that this water was absorbed by the quartz flour and not 
by the sand. The quartz flour might then hold the water with 
sufficient force to prevent its return to the cells of the lips and 
thus not allow them again to become turgid. If this explanation 
is correct, movement would seem to be due to causes similar 
to those operative in the case of Mimosa. Here ^ there appears 
to be a reduction in the turgor of the cells of the concave half 
of the pulvini, which cells are probably compressed by those 
of the opposite turgid half. 
The lips of the stigmas are usually much less sensitive on the 
day that the flowers open than on the two or three days following. 
They also spread apart much more slowly after closing, this 
process frequently requiring a number of hours. On the fourth 
or fifth or, sometimes, even on the third day they again become 
* Brown, W. H., and Sharp, L. W. The Closing Response in Dionaea. 
Bot. Gaz. 49 (1910) 290-302. 
* Brown, W. H. This Journal 7 (1912), Botany, 37. 
