1913.] PUBLIC DOCUMENT — No. 31. 85 



can Association for the Advancement of Science on potato scab, 

 which was published in the September and October number of 

 ''Agricultural Science" the same year, and he established that 

 " (1) the disease is of parasitic origin; that (2) it is for the 

 most part conveyed to the growing crop by infection from the 

 tubers used as seed; that (3) much of the so-called 'smooth 

 seed ' is in reality infested with the germs of the disease ; and 

 that (4) planting seed tubers free from disease germs gives a 

 crop practically without scab." ^ 



His researches and experiments proved to be a great step in 

 advance. V/hile he apparently did not discover the true nature 

 of the organism he paved the way for investigations on the 

 prevention of the disease.- 



The results of Dr. R. Thaxter's investigations, which were 

 carried on in 1890, v/ere read before the Association of Agri- 

 cultural Colleges and Experiment Stations N^ovember, 1890, 

 and later were published in a report of the Connecticut Experi- 

 ment Station. Ilis work largely confirmed that of Professor 

 Bolley. He isolated and cultured an organism with which he 

 was able repeatedly to successfully inoculate potatoes and pro- 

 duce the typical scab, although the organism was different from 

 that described by Professor Bolley. It should be noticed that 

 both Professor Bolley and Dr. Thaxter were working on the 

 same lines unknown to each other, and made their results public 

 at nearly the same time, each having arrived at similar conclu- 

 sions as to the cause of the scab. The organism which Dr. 

 Thaxter isolated was not a bacterium but a low form of fungus 

 possessing more or less indefinite relationships. He later named 

 this, Oospora scabies. Although this organism has been isolated 

 and studied by only a few other pathologists, it is generally 

 recognized that it is the principal if not the only organism asso- 

 ciated with the scab. It would not be at all unlikely that the 

 bacterium which Professor Bolley isolated is capable of produc- 

 ing a form of scab ; nevertheless, from the viewpoint of treat- 



« J. C. Arthur, Bui. 56, Purdue Univ. Agr. Exp. Station, 1895. 



2 Professor Bolley was thoroughly convinced that potato scab was caused by a pathogenic 

 organism, and from the first made use of corrosive sublimate in his experiments. He was unfortu- 

 nate in having very poor material to work with, and informs me that the .soil was badly contami- 

 nated with the scab and bacteria. Dr. Thaxter observed the fungus growing on the surface of 

 the potato, but Professor Bolley failed to find this, although he found plenty of bacteria. 



