250 



COLLEGE BOTANY 



tion as worked out by Darwin, Mendel, DeVries and other more 

 recent students of the subject. 



Bacteriology dates from the work of the great French scien- 

 tist, Pasteur (Fig. 115). It involves the study of the very 

 minute organisms, which are probably the lowest of the fungi. 

 Some of these organisms are extrpmely important factors in soil 

 fertility and therefore it is very closely associated with agri- 

 cultvire; other organisms are the cause of diseases of man and 

 beast and therefore it is closely associated with the study and 

 practice of medicine; other organisms are 

 the cause of diseases of plants and there- 

 fore it is closely associated with the study 

 of plant pathology; while still others 

 are of impo'rtance in the .manufactur- 

 ing industries. 



Plant p'oihology deals with the causes 

 and treatments of plant diseases. For 

 many years it was studied .by two entirely 

 different groups of workers, the mycologist, 

 who was interested primarily in the causal 

 organism, and by the grower, who was interested in the protec- 

 tion of his crops. Little progress was made under these conditions, 

 but finally the subject was taken up in a more comprehensive 

 manner by the botanists and is now recognized as one of the most 

 important branches of botany. It involves a careful study of the 

 organisms causing the diseases, their effect on the host plant and 

 the methods of eradication or control. The object of plant pathol- 

 ogy is primarily the increase of plant production by the protection 

 of valuable plants from their enemies. It Is very closely corre^ 

 lated with plant physiology, agronomy, horticulture and forestry. 



Fig. 115. — Pasteur. 



