

304 BOTANICAL GAZETTE [april 



of the field and of the diversity of research material. It is evident 

 that no one person, either by temperament, inclination, or equip- 

 ment, is fitted to investigate in all of these fields. The range is 

 broad, and with a veritable wealth of research material, and a 

 survey of the past shows that the well worked subject often is 

 just as productive of results as an apparently much fresher subject. 

 For years the powdery mildews have been introductory subjects 

 in mycology. The group has been thoroughly monographed, col- 

 lected, listed, years devoted to their biological specialization, 

 treatments devised, etc. The field appeared too thoroughly 

 worked to be promising of large results; yet recent studies have 

 revealed the bud-scale hibernation habit of certain of these, and 

 thus added fundamental knowledge useful in prophylaxis. 



Finally, the diseases themselves, not the fungi, need classifica- 

 tion. Various classifications have been used, as to cause, as to 

 host, etc., but these do not serve to emphasize relationships of 

 conditions w r hich it is of service to know. 



Aside from the non-parasitic diseases, those caused by improper 



abnormal 



unknown 



and considering only those known to be caused by parasitic fungi, 

 there are certain groups of conditions which stand out strongly 

 marked as being similar. It is of distinct advantage in studying, 



m teaching, and in devism 

 nize and define these catep- 



similarity 



diseases have gravitated together; for example, the vascular 

 diseases, fungous or bacterial diseases, with plugging of the bundles, 

 popularly and very properly call the "wilts." 



It is interesting to note that one of the most significant con- 

 tributions along this line appeared in one of our elementary texts; 

 significant, too, that this contribution should come from one not 

 primarily interested in pathology. Coulter, in his Elementary 

 studies in botany, gives us the conception of three general categories 

 of plant diseases: (i) those in which the narasites kill the living 



mi 



in which the parasite does not kill the living 



in association with them 



as 



tliose in which 





' 



