Notes. 
363 
convex side become more, and those of the concave less turgid than 
before. Some time after stimulation, and when the period of aggre- 
gation has set in, it can be observed that the cells of the convex side 
are less aggregated than those of the concave. Having ascertained 
that of the dye solutions, eosin, and of salts, the salts of ammonia, 
are readily sucked up into the tissue, it was further noticed that in 
stimulated tentacles the cells of the convex side readily allow the 
solutions to penetrate, while those of the concave are only penetrated 
with great difficulty. Thus in the case of a stimulated tentacle 
treated with eosin, the convex cells are stained long before the con- 
cave, and with ammonic carbonate the tannin of the convex cells may 
be precipitated while the concave cells remain normal, or the convex 
cells may even be killed while the concave cells remain alive. Thus 
after stimulation certain changes have occurred in the concave cells 
of the bending portion, and one result of this change is an increased 
impenetrability of the primordial utricle. In my earlier paper I 
have shown that the tentacle cells of Drosera are very sensitive to 
contact, for if the gland-cells be slightly crushed, all movement of the 
stalk-cells ceases for a time, and the spindle-shaped rhabdoid contracts 
and tends to become spherical. Bearing in mind also the very pro- 
nounced inflection which is occasioned by the stimulus of contact or 
food, by electrical stimulus or, as Darwin has shown, by the stimulus 
of temperature, one is led to ask whether these phenomena are not 
associated with true contractility, and whether the increased impene- 
trability of the protoplasm of the concave cells is not occasioned by 
a definite contraction of the primordial utricle and a consequent 
decrease in the size of the molecular pores. 
Experiments were then made upon the pulvinus of Mimosa pudica . 
Small pieces of stem (bearing leaves) were cut under a watery solution 
of eosin, and the pulvini were maintained in a state of stimulation. 
When the eosin had sufficiently penetrated, transverse and longi- 
tudinal sections of the pulvinus were made and examined. It was 
then seen that the dye had readily penetrated into and stained the 
protoplasm of the outer cells of the convex side of the pulvinus, 
while on the concave side no staining whatever, of that tract of cells 
situated towards the more external portion, which especially play an 
active part in movement, had taken place. The more indifferent cells 
immediately surrounding the vascular bundle also show some contrast 
in coloration, for in the upper half this tissue remains unstained, 
c c 
