attitude; op pathologists and bacteriologists. 17 



Nadson's Russian paper, published in 1899, is a popular account drawn from the 

 literature of the subject. He admits the existence of plant diseases due to bacteria. 



-In his Text-book of Plant Diseases, published in 1899, Massee devotes 4-J- pages out 

 of 470 to bacterial diseases, mentioning bacteriosis of tomatoes, hyacinth bacteriosis, pink 

 bacteriosis of wheat, black-rot of cabbage, olive tuberculosis, and the brown-rot of tomato, 

 eggplant, and potato. The author's perfectly safe standpoint is expressed in the following 

 words: "At the present day numerous plant diseases are attributed to bacteria, some 

 truly, others doubtfully so." 



Out of 1,350 odd species considered in the second volume of Migula's System (1900), 

 30 are at present of more or less interest to the plant pathologist. The action of the 

 remainder, when introduced into living plants, is nil or unknown, mostly unknown. This 

 book, like the Sylloge Schizomycetum of De Toni and Trevisan in Saccardo's Sylloge 

 Fungorum, is devoted to a description of species rather than to a consideration of their 

 pathogenicity. 



The last yiews of Hartig, which did not differ very materially from those held by him 

 20 years earlier, are sufficiently illustrated by the following quotations from his Lehrbuch, 

 published in 1900: 



In fact, bacteria have been found thus far only in the tissue of those plants the cells of which 

 are of a parenchyraatic nature or are very thin-walled, as in bulbous and tuberous plants. 



The yellow disease of hyacinths is erroneously ascribed to onions and is further dis- 

 cussed as follows : 



The bacteria do not attack sound well-ripened bulbs under normal conditions. Some sort of 

 wounding is necessary, such as readily occurs during the lifting of the bulbs and their storage in 

 another place, or else the bulbs are already attacked by fungi, among which a Hyphomycete in par- 

 ticular is an almost constant accompaniment of the rot disease. In a damp situation the bacteria 

 force their way into the wound and cause its decay. 



Bacteriosis of the potato is dismissed with 6 lines upon "wet-rot of the tubers." Pear- 

 blight is discussed in 4 lines; sorghum-blight is mentioned in 6 lines. 

 Of the olive tubercle it is said : 



In the olive forests gall-formations from the size of a pea to that of a walnut often occur in 

 enormous numbers. These galls soon die and show in the crevices [of the dead galls!] large bacterial 

 masses (figs. 203 and 204). But whether these are the cause of the gall-jormations is not yet proved. [The 

 italics are mine.] 



No other diseases are mentioned and this chapter closes with the following paragraph : 



Recently still other diseases have been ascribed to bacteria, without, however, furnishing the 

 convincing proof by means of infection experiments that the Schizomycetes are the cause of the 

 diseases. With these belong also the slime-flows of trees. 



In December 1900, Erwin F. Smith gave a lantern-slide lecture in Baltimore, Maryland, 

 before a joint session of the Society for Plant Morphology and Physiology, and the Society 

 of American Bacteriologists, illustrating fully three bacterial diseases from original photo- 

 graphs and photomicrographs in his possession (Science, February 15, 1901). 



Weiss (1901) mentions, as of bacterial origin, wet-rot of the potato, white or yellow 

 rot of hyacinth bulbs, beet-tip rot, and scab of potatoes. 



Less important bacterial diseases are probably — rot of onions, rose-red wheat kernels, * * * 

 and the mosaic disease of tobacco. 



This author's standpoint is expressed in the following introductory remarks : 



The plant diseases due to Schizomycetes are of subordinate importance, while the bacterial 

 diseases of animals and men are of the greatest importance. The bacterial diseases of the cultivated 



