ON DROSERA ROTUNDIFOLIA pas 
In all cases of direct stimulation of the gland, the bending of 
Drosera tentacles is nastic; the inflected gland always points 
toward the center of the leaf. The stimulus may be contact, 
heat, injury or some chemical substance in solution. 
When a tentacle reacts to a single stimulation, it begins to 
unbend immediately after the ultimate degree of inflexion has 
been reached. This is the case when the gland has been irritated 
by contact with some object for a limited space of time. If the 
source of stimulation is not removed, as for example when an 
insect is caught and digested, the tentacle remains inflected for a 
period varying from one to eleven days, according to C. Darwin 
(’o8, pp. II, 195). During the interval between bending and 
unbending the tentacle does not grow in length. 
ii. Unbending 
The unbending of the tentacle is accompanied by an increase 
in the rate of growth on the concave side and in the median section. 
The convex side always contracts so that the so-called neutral 
line exists somewhere between it and the middle of the tentacle. 
The acceleration of the rate of growth is characterized by a trans- 
verse distribution which is exactly opposite that accompanying 
bending. Its longitudinal distribution is however identical. The: 
increase in the rate of growth commences opposite that basal 
portion of the convex side which reacted first, and extends as far 
apically. Growth is most rapid near the base and becomes less 
intense toward the gland. The contraction of the convex side 
is usually restricted to a short basal region. 
It frequently happens that the concave grows less than the 
convex side, since the latter is compressed during the expansion of 
the tentacle. The concave side may undergo a certain amount of 
compression during the inflexion of the tentacle, so that the two 
sides grow and contract approximately equal amounts. The 
unbending proceeds much more slowly than the bending. 
In all probability the unbending of Drosera tentacles is auto- 
tropic (cf. Fitting, ’03, p. 612). The stimulus perceived is the 
inequality of conditions, pressure, tissue-tension, etc., which is 
produced on the opposite sides of the originally straight tentacle 
by its bending. The unbending is therefore of a tropic nature, 
