COOK: MODERN APPLICATIONS OF BOTANY 125 



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 \alue 

 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 

 in\'estigations 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- 



