22 
SENSITIVE PLANTS. 
By maxwell T. MASTEES, M.D., F.L.S. 
A natomists and physiologists, both alike interested in 
studying the manifestations of life, the one studying the 
working, the other the organisation of the machine, have natu- 
rally turned their attention to the vegetable world, in the hopes 
that the simpler structure of plants would yield a clue towards 
the deciphering of many a problem in animal physiology. The 
physiologist, by the careful observation and comparison of the 
several organs in various groups, from the highest to the lowest, 
has been enabled to make great strides towards a right under- 
standing both of structure and function. The machine has been 
pulled to pieces, and its action has to a great extent been eluci- 
dated. What more natural than to suppose that a similar process 
carried on in the case of plants would lead to analogous results ; 
and yet the present state of vegetable physiology is often said 
to bear unfavourable contrast to that of the animal kingdom. 
It can hardly be said that the vegetable physiologists are less 
active than their colleagues, or that their means and appli- 
ances are inferior. What, then, is the reason for the alleged 
greater proportionate advance of the one than of the other de- 
partment of the history of life ? The main reason, as has been 
often pointed out, is the comparative simplicity of plant structure 
as compared with that of animals. It is comparatively easy in 
the case of the latter to assign a particular use to a certain 
organ having a certain structure, or occupying a definite posi- 
tion. All this is a matter of easy observation ; but in the case 
of plants we find organs, to all appearance, essentially the same 
as to structure performing widely different functions. If a 
student of the animal kingdom saw the same organ perform- 
ing at one time the functions of absorption, of exhalation, and 
of secretion, he would be as much embarrassed as a botanist 
is when he comes to investigate the functions of the leaf. 
And after all, when the matter comes to be sifted down, there 
is no such great difference between animal and vegetable 
physiology as to their relative status. In the presence of the 
cell, simple enough in its structure, but widely diverse in its 
mode of action in different cases, the physiologist, whatever 
