372 BACTERIAL DISEASES OF PLANTS 



mained sterile. In a repetition of the experiment there was no 

 clouding either at 45 or 46C. As a rule it lives long on culture 

 media. Drying on cover glasses up to 5 days has no appreciable 

 effect (L. R. Jones, D. H. Jones). Tolerates HC1 in bouillon 

 (+4) up to +16 and NaOH down to -6 (D. H. Jones). Opti- 

 mum reaction for growth + (D. H. Jones). It resists freezing 

 fairly well. In tests made in 1919, 15 per cent survived. It 

 is identified readily by its behavior under bell jars, when streaked, 



FIG. 287. Pear blight: A detail from one of the cavities shown in Fig. 286. 



on raw green pears, which should rot; and on ripe ones, which 

 should not rot (Waite's method). This test may be made also 

 in late winter or early spring (in advance of the growing season) 

 on vigorous shoots of the pear by bringing them into a warm 

 room and standing the lower parts in a jar of water until they 

 have begun to sprout (Waite's method, verified by Katherine 

 Golden). Then with a sharp knife remove the tops making a 

 slant stroke, on which should be rubbed the organism to be 

 tested. If it is a virulent strain of Bacillus amylovorus, the 



