1895.) Development of Vegetable Physiology. 399 
the processes by which the organism communicates with the 
world outside of itself, and through which it is enabled to ad- 
just itself to environmental conditions, the processes which in 
their highest development are known as sensations, have at- 
tained great differentiation, running along essentially differ- 
ent lines of development. The prevalent view that plants 
occupy an intermediate position between the mineral and the 
animal kingdoms is not true in any important respect. Neither 
is it true that the faculties of animals, especially of the lower 
animals, are foreshadowed in plants. No just conception of 
animate nature can be obtained by conceiving it to lie in a 
single ascending series. It constitutes two diverging and 
branching series, like the blades and stems in a tuft of grass, 
which we may assume have been derived from a common 
germ. There are two fundamental characters which mani- 
fested themselves early in phylogenetic development, one 
structural and one physiological. The structural character 
of the histologic integument of the organism, in animals soft 
and highly elastic, in plants firm and but slightly elastic, gave 
rise to the two series of forms, structurally considered, which 
we call animals and plants. The physiological character of 
free locomotion for most animals and a fixed position for most 
plants, determined the line of separation for the development 
of those powers of the organism classed as irritability and sen- 
sation. So great have been the differences which these funda- 
mental characters have brought about, that the stimulating 
action of external agents, such as light, heat, and gravity, 
have produced very diverse powers in the two kingdoms. 
Animals have a wonderful mechanism which enables them to 
see, while plants have a no less wonderfully specialized sensi- 
tiveness by which they assume various positions to secure 
more or less illumination. Animals have a sense of equipoise, 
but plants have a very dissimilar and even more remarkable 
sense of verticality. And so on throughout the list of stimuli, 
the reactions are not the same, but are differentiated along 
entirely separate and divergent lines. The period is fortu- 
nately well past when physiology was chiefly cultivated with 
an arriere pensée as to its value for interpreting the functions 
in man, and hence, in claiming for this department of study 
the most exalted position, and the most intricate and inter- 
esting of botanical problems, we need not be distracted by 
any lurking cui dono, or feeling of having come short of ample 
