136 The Department of Plant Physiology [3384 
are classified and identified are physiological, since the 
processes induced by these minute organisms happen to be 
more easily observed than are their structural differences. 
Application of Physiological Science—Just as physics, 
chemistry, climatology and biological morphology become 
applied in physiology, so does physiology become applied in 
many other lines of human activity. As with other sciences, 
there are, in general, two groups of applications that are pos- 
sible. First, there is the general application of physiologi- 
cal knowledge and principle to the formation of what has 
been called a “philosophy of the universe.” This is perhaps 
its application as “pure science,” and for this application 
plant physiology is almost, if not quite, as valuable as is 
animal physiology. Such application is not usually called 
an application at all, not being primarily practical for the 
physical aspects of human life, in the sense of “buttering 
bread.” But there are still men who do not live by bread 
alone, and a commercial age has not yet proved that a gen- 
eral appreciation of the relations of the things about us may 
not be ultimately as valuable to the human world as are 
those things which money buys directly. It is in this direc- 
tion of application that modern natural science claims at 
least an equality with philology, history and the other 
humanities. 
The second group of applications possible for physiologi- 
cal science includes those commonly called practical, by which 
food and clothing and dwellings may become more readily 
available to human beings, and by which human health and 
comfort may be enhanced. Just as animal physiology finds its 
most numerous applications of this sort in the fields of medi- 
cine, surgery, hygiene, animal husbandry, etc., so plant physi- 
ology contributes most to human physical welfare in the 
fields of agriculture, forestry, fermentation operations, bac- 
teriology, etc. These applications are more interesting to 
more persons than are those of the first group and their 
importance is not to be minimized. Indeed, the more a sci- 
ence may be practically applicable the more opportunity it 
may have for becoming philosophically applicable. The two 
