412 VEGETABLE PHYSIOLOGY 
differences in hygrometric condition, though nothing 
anatomical suggests such diverse powers. If such a sensi- 
tive organ is acted upon at the same time by two stimuli 
which usually produce opposite movements, the resulting 
position is always such as would be caused by the greater 
influence of the stronger of the two. The organ is, in fact, 
able to receive both stimulations simultaneously, and to 
respond to each as if the other were not received. 
If we turn to the second feature of the nervous system, 
we find that the motor mechanism of the plant seems at 
first to be entirely different from that of the animal. 
Closer consideration, however, lessens the difference con- 
siderably. The motor mechanism of an animal is nearly 
always either muscular or glandular. The vegetable 
cell seems to have much more in common with the gland 
cell of an animal than with its muscles. Stimulation of a 
nerve going to a gland frequently causes a flow of liquid from 
the latter, probably owing to a change in the permeability 
of the protoplasm of the gland-cells. The contractile 
power is but little developed in vegetable protoplasm, and 
when present it seems to be rather passive than active, 
to be associated with recoil rather than true contraction. 
Still, the latter is not entirely absent. We have seen that 
it can be detected in the pulsation of vacuoles, in ciliary 
motion, and in the crawling movements of the Myxomycetes. 
Though the power of contraction is comparatively 
seldom found, the action of the gland-cell is recalled by the 
power which vegetable protoplasm possesses of resisting or 
assisting the transit of water. The effect is really similar in 
both cases; in the animal the disturbance to the protoplasm 
leads to a contraction of its substance, in the plant to its 
lessening its resistance to the passage of water through 
it. Each protoplasm responds in its own appropriate 
fashion, which is based upon the need of the organism of 
which it is part. The main requirement of most animals 
is freedom of locomotion or rapid assumption of new posi- 
tions by the body. The most important duty of the plant is 
