168 PLANT PATHOLOGY 



botanical microchemistry, as well as the studies of fungicides, 

 bring the science of chemistry into continual use in pathological 

 work. In fact, the limitations of the working bacteriologist and 

 pathologist of to-day are largely in knowledge of chemistry. Most 

 pathologists acknowledge that they have too little training in chem- 

 istry for the best results. The knowledge of theoretical chemistry, 

 especially organic chemistry, is imperatively demanded in the further 

 advancement of plant disease investigation. Perhaps no branch 

 of natural science is of more use to pathologists at the present stage 

 than physiological chemistry. It is opening the doors to entirely 

 new fields of investigation in plant diseases. The general methods 

 of research and laboratory equipment of the chemist are in frequent 

 use by the pathologist. 



A knowledge of physics is also of the utmost use to the working 

 pathologist. While he can scarcely be expected to make investiga- 

 tions in the physical composition of soils, yet he must be prepared 

 to utilize and understand the results obtained by workers in that 

 line. We now know with more certainty than ever that many of 

 the physiological processes in plant life are directly attributable to 

 physical laws. 



The plant pathologist should also have a general knowledge of 

 horticulture and agriculture, or at least agronomy. He should 

 understand the cultivation of plants, and should be prepared to 

 master quickly and thoroughly the culture of any specific plant 

 when occasion demands. 



I have attempted to show that, while vegetable pathology is a 

 somewhat narrow specialty, it requires very broad training on the 

 part of the investigator. An ideal pathologist should have a thorough 

 knowledge of systematic botany, including mycology, of physiolog- 

 ical and anatomical botany, of cytology, ecology, and bacteriology, 

 as well as a knowledge of zoology, entomology, chemistry, and 

 physics, and allied sciences. I need scarcely mention that he should 

 also have a good preparation in the languages, especially German, 

 French, Italian, and Latin, and in such incidentals as drawing, 

 photography, photomycrography, etc. A knowledge of horticulture 

 and agronomy becomes absolutely essential when he starts in field 

 work. Such a pathologist, of course, scarcely exists. Such com- 

 plete equipment is hardly to be expected in one individual. No 

 one realizes their deficiency more than the pathological workers 

 themselves. 



The Treatment of Plant Diseases 



The object of an investigation of a plant disease is to find out 

 the cause and remedy. If it is a parasitic disease the nature and life- 

 history of the parasite must be determined. Its complete life-his- 



