8 BACTERIA IN RElvATION TO PLANT DISEASES. 



leaves with a yellow organism, the disease progressing in just that slow regular way described 

 by Wakker as a result of his own inoculations. Wakker worked at that time in the labor- 

 atory of Hugo de Vries in Amsterdam, under a royal grant obtained by the hyacinth 

 growers of Haarlem. Afterwards, for five years, he was in charge of one of the Javan sugar 

 experiment stations. He has published various papers on fungous and other diseases of 

 plants, those of recent years being devoted largely to the sugar-cane. 



Comes was one of the earliest workers in this field. He recognized bacteria in the 

 tissues of various diseased plants in southern Italy as early as 1880, and published a 

 number of papers on Bacterium gummis, which he believed to be a widely distributed para- 

 site attacking many plants. He did not, however, grow the organism properly in pure 

 cultures and secure infections, nor describe it so that one can now be certain of its identity. 

 He early turned his attention to other subjects, much of his energy being given to teaching 

 botany in the Royal Agricultural College at Portici, of which he is now director. He is 

 the author of a general text-book on botany, of a book on diseases of plants, and of elabor- 

 ate treatises on tobacco, as well as of numerous minor publications, and his students are 

 scattered all over Italy. He seems never to have had any doubt as to the occurrence of 

 bacterial diseases in plants. 



Sorauer also being one of the voluminous writers on plant pathology should be men- 

 tioned here, because, as early as 1886, he saw clearly that Wakker and the others were right. 

 Sorauer regarded the bacterial diseases of plants ony from the general standpoint of a 

 writer and student of plant pathology. He examined various such diseases microscopi- 

 cally but did not make pure cultures or inoculations therefrom, not having had the neces- 

 sary grounding in bacteriological technique. He endured much obloquy in his earlier years 

 for steadily maintaining the existence of such diseases in opposition to Hartig and his 

 school, but he has lived to see his contentions established. Sorauer is the author, among 

 other works, of the most elaborate and important German handbook on diseases of plants, 

 the third edition in three volumes having been completed recently. He is also the founder 

 and editor of the Zeitschrift fiir Pflanzenkrankheiten. 



Savastano and Arthur began work a little later than the others when there were not 

 so many difl&culties in the way. 



Savastano conceived the idea that the olive-tubercle was caused by bacteria. He 

 demonstrated the constant occurrence of bacteria in the knots, isolated them therefrom in 

 culture-media, and produced typical overgrowths on healthy olive shoots by punctures into 

 which minute quantities of the culture were inserted. Cavara went over Savastano's experi- 

 ments soon afterward with similar results, and the writer and his assistants have done the 

 same thing in recent years (see vol. I, plate 2). This was Savastano's most important 

 incursion into bacteriology. He described, however, in an imperfect and fragmentary way 

 a number of other diseases as bacterial, most of which are really such. He is the author of 

 a handbook, Patologia Arborea Applicata, and the editor of the BoUettino della Arboricol- 

 tura italiana. Savastano held for many years the chair of forestry in the Royal Agricultural 

 College at Portici and is now director of the experiment station at Acireale in Sicily. 



Arthur repeated and verified Burrill's work on pear-blight and carried the investiga- 

 tions somewhat further, demonstrating that infectious fluids filtered through porous clay 

 cups lost their power to produce the disease, whereas the residue containing the bacteria 

 was as infectious as ever. Arthur began his experiments about the time that Burrill ceased, 

 and continued them for a number of years, pubhshing a half dozen papers on pear-blight 

 and the organism to which it is due, these papers forming his most important contribution 

 to plant bacteriology. He was at that time stationed at the Geneva experiment station 

 in central New York. Since then he has been professor of botany in Purdue University, 

 Indiana, and has published interesting papers on fungi and other plants. He is the author, 

 with Barnes and Coulter, of A Handbook of Plant Dissection and has published with 



