On 
COOK: MODERN APPLICATIONS OF BOTANY 12 
Plant growth is no longer a problem for chemists but for the 
plant physiologist, who is trained not only in botany, but in chemistry, 
physics and geology. Plant physiology has outgrown the expectations 
of its most enthusiastic devotees of a decade ago, and no one can 
foretell its future. It will doubtless result in important changes in 
agricultural methods. 
Plant breeding, along the lines of artificial selection, is very old; 
in fact, it must have originated with the first steps in civilization. 
Many of our valuable economic plants were selected, grown and 
used by man before the beginning of written history and many im- 
proved varieties have been developed by self-taught, practical workers, 
men of great natural endowments and keen powers of observation. 
However it is none the less true that they are the products of the 
workings of natural laws and that a knowledge of these laws enables 
the present generations to work more rapidly than their ancestors. 
Many of our modern plant breeders are very properly more interested 
in researches leading to a knowledge of these laws than in their appli- 
cation. A law fully established and well understood will very soon 
be utilized by those interested in increased production. But the 
breeder should not loose sight of the very great value of plant breeding 
to agriculture. The final and true standard of measure of the value 
of any science must be in terms of its contributions to the welfare of 
mankind. 
Plant pathology is one of the last of these branches of applied 
botany to be considered. It had its rise in the taxonomic study of 
fungi, many of which were recognized as the causes of plant diseases. 
Therefore, this study very naturally led to the study of methods of 
control. Indefinite and uncertain methods for the control of plant 
diseases have been used from time to time for more than a century. 
But a lack of definite knowledge of the causes and the physiology of 
these diseases and the actions of the remedies made the results very 
uncertain and very soon led to their disuse. 
Modern plant pathology had its beginning in the works of de Bary 
and Berkeley, but did not make much progress until the latter part of 
the last century. The progress during the last decade has been rapid 
and has emphasized the necessity of many lines of study, such as a 
more thorough knowledge of the life history and taxonomy of the 
parasites, a knowledge of the physiological factors influencing both 
host and parasite and a knowledge of the physiological effects of the 
fungicides. It is also extremely important that we make extensive 
investigations on that ever increasing number of diseases which cannot 
at this time be attributed to any definite organism. 
The prosecution of these lines of investigations means more in- 
