394 BACTERIAL DISEASES OF PLANTS 



in a variety of media and yet is not absolutely identical. With 

 it we have produced typical small cankers on American and Euro- 

 pean species of ash, especially on the European Fraxinus ex- 

 celsior, but no tumors on the olive although repeated inoculations 

 were made on young olive shoots both in 1914 and 1915. The 

 ash organism, therefore, should be regarded probably as a 

 variety of Bacterium savastanoi rather than as identical with the 

 olive organism, or as a distinct species, but further studies and 

 comparisons should be made. 



The oleander in Europe and in some parts of the United 

 States is also subject to a bacterial overgrowth on leaves and 

 shoots, which by various observers has been thought to be due 

 to the same organism as the olive tubercle, but my observations 

 and inoculation experiments lead me to think it is not due to the 

 olive-tubercle organism. This is also Petri's opinion. 



Cause. — In 1886 Archangeli described the olive tubercle, 

 giving the name Bacterium oleae to something observed in it 

 but without what we should now consider to be a proper de- 

 scription, i.e., it was named from the microscope, without cultures 

 or proofs of its infectiousness by inoculation, and with the state- 

 ment that it probably had nothing to do with the disease, which 

 was ascribed by him to other causes. Savastano's inoculation 

 experiments (1887-1889), repeated and confirmed by Cavara, 

 first proved the olive tubercle to be due to bacteria, but neither 

 one of these men described the organism sufficiently. Savastano 

 called his cultures Bacillus oleae-tuherculosis, but, following Tre- 

 visan, systematic writers generally have spoken of Bacillus 

 oleae (Arch.) Trevisan as the cause of the olive tubercle. Subse- 

 quently Schiff-Georgini isolated and described very carefully 

 a non-infectious, white, spore-bearing, peritrichiate, filamentous, 

 potato bacillus from the olive-tubercle, called it Bacillus oleae 

 (Arch.) Trev., and claimed to have obtained tubercles repeatedly 

 by inoculating it into olive shoots (1905). On the contrary, 

 Berlese (1905) considered a yellow organism isolated by him 

 to be Bacillus oleae (Arch.) Trev., and the cause of one type of 

 olive tubercle. Several saprophytes occur commonly in olive 

 tubercles, one of which at least is yellow, i.e., that seen by Ber- 

 lese. Savastano must also have had a yellow organism in some 



