148 The Department of Plant Physiology [346 
relation (besides its consideration as a term in the water- 
relation). The complex relation holding between plant 
growth and what is generally understood by the vague word 
climate, also enters into some of our more recent undertakings. 
This is not the place to attempt a presentation of the de- 
tailed results so far obtained in the research work of the Lab- 
oratory of Plant Physiology, although it may be remarked that 
some apparently valuable results have already rewarded our 
efforts. What most requires emphasis here is, however, that a 
large amount of necessary preparation has been accomplished, 
getting ready for rational experimentation in the future. 
Many new methods of operation and of interpretation have 
neen evolved, and it appears as though the time may not be 
remote when some of the broader aspects of the conditional 
control of plant activities may be undertaken with some prom- 
ise of a satisfactory outcome. Such broader problems will 
probably have to be left to other institutions, with more facili- 
ties and larger appropriations than are now generally avail- 
able for university laboratories. 
To summarize the last few paragraphs, our operations have 
been and are directed toward a dynamic analysis of plant 
activity. The point of view here employed may perhaps be 
envisaged if the reader will regard the living plant in some- 
what the same general way as he might any complex machine, 
such as a gasoline motor, for example. To understand its 
working one must understand how and how much various con- 
ditions may affect such a machine; in short, he must become 
an engineer with respect to that particular mechanism. Dyna- 
mic plant physiology may be said, then, to be engineering sci- 
ence as applied to the operations of the living plant. It can 
progress only through quantitative studies,—through experi- 
mental tests under controlled or measured conditions, through 
the comparison of efficiency graphs and curve-tracings made 
by recording instruments, through the mathematical interpre- 
tation of relations between conditions and process rates, 
ete..—and it is with just this sort of studies that our inves- 
tigations have to do. 
