RESEARCH IN PHYTOPATHOLOGY 209 



elucidation. With a knowledge of the fact that nutrition may 

 so alter a facultative saprophyte that it becomes a virulent 

 parasite, while through other nutritional changes its virulence 

 may be entirely lost, and further that the same influence 

 operates in rendering the host more or less susceptible, we 

 have the key to one of the important determining factors in 

 the epidemic diseases of plants. It is no longer sufficient to 

 trace life-histories or to prove parasitism under certain special 

 conditions. The nutrition of both host and parasite must be 

 taken into account, together with other factors which tend to 

 disturb the nice balance existing between health and disease. 

 We must look to further investigation in the botanical laboratory 

 and in the field, for a solution of these and other problems 

 connected with Plant Pathology. 



Literature 



Archangeli, "Sopra la malattia dell'Olivo volgarmente Rogna," Pisa, 1886. 

 Arthur, "Annual Report of the New York Agricultural Experiment Station," 



1884, 1885. 

 Bernheim, Die parasitaren Bakterien der Cerealien, Munchc?icr Medicinische 



Wochenschrift, 1888. 

 Brefeld, Methoden zur Untersuchungen der Pilze, VcrJiandlimgC7i der 



Physikal-Medicin GescUschaft in IVurzburg, Bd. viii., 1875. 

 BUCHNER, Notiz betreffend die Frage des Vorkommens von Bakterien im 



normalen Pflanzengewebe, Miinchener Medicinische IVochenschri/f, 1888. 

 BURRI, Die Bakterienvegetation auf der Oberflache normal entwickelter Pflanzen, 



Centralblatt fiir Bakferiologie^ Abt. ii., Bd. x., 1903. 

 Cobb, Plant Diseases and their Remedies, Department of Agriculture, Sydney, 



New South Wales, 1893 ; Kciu Bulletin, 1894. 

 COHN, Untersuchungen iiber Bacterien, iv., Beitrage zur Biologic der Bacillen, 



Beitrdge zur Biologic der Pflanzen, Bd. ii , 1877. 

 DE Bary, " Comparative Morphology and Biology of the Fungi Mycetozoa and 



Bacteria," English Edition, 1887, p. 481. 



, "Lectures on Bacteria," English Edition, 1887. 



Dl Vestea, De 1' Absence des Microbes dans les tissus vegetaux, Annates de 



rinstitut Pasteur, 1888. 

 DiJGGELl, Die Bakterienflora gesunder Samen und daraus gezogcner Keim- 



pflanzchen, Centralblatt fiir Bakteriologie, Abt. ii. , Bd. xiii., 1904. 

 Fernbach, De 1' Absence des Microbes dans les tissus vdgdtaux, Annates de 



r Institut Pasteur, 1888. 

 Fischer, "Structure and Functions of Bacteria," English Edition, 1900, p. 137. 

 Frank, Untersuchungen iiber die verschiedenen Erreger der Kartoffelfaule, 



Berichte der Deutschen Botanischen Gcsellschaft, Bd. xvi., 1898. 

 Galippe, Note sur la Presence de Micro-organismes dans les tissus v(?getaux. 



Journal des Connaissanccs viddicales, June, 1887. 



