A Bacterial Disease of Stone Fruits 



399 



good results. The flagella were also stained without a mordant, by- 

 exposing the covers to carbol fuchsin for from twenty-five to fifty minutes 

 and carefully washing in alcohol (Fig. 67). 



Capsules. — Capsules have frequently been stained in material obtained 

 from Uschinsky's solution by both Welch's and Moore's methods. 



Zooglosce. — Zoogloese are fre- 

 quently found on various media. 



Involution forms. — No involu- 

 tion forms have been observed. 



Staining reactions. — The organ- 

 ism stains readily with the ordi- 

 nary aqueous stains — aniline 

 gentian violet, and carbol fuchsin. 



Gram's stain. — Many efforts at 

 staining were made with Gram's 

 method, but the results were not 

 sufficiently sharp and decisive to 

 warrant a conclusion. In no case 

 was the stain completely lost, nor 

 was it ever retained in the orig- 

 inal intensity. The aniline gentian violet and iodine solutions were used 

 for two minutes and the preparations were left in absolute alcohol for 

 three minutes. In no case were the mounts washed in alcohol as intensely 

 stained as those not treated with alcohol, and consequently the organism 

 must be regarded as Gram negative. 



Acid-fast. — The organism is not acid-fast. 



Cultural characters 

 Source of cultures. — Eighteen strains were used for each test, one 

 from the apricot, one from the nectarine, nine from the peach, and seven 

 from the plum. The reactions of all the strains on the various media 

 were uniform, and no marked differences were observed except in one of 

 the plum strains, which invariably grew most rapidlj'-. The growth of 

 this strain on potato plugs was more abundant than that of any of the other 

 strains. Its growth on Hiss-glucose was often a number of hours in advance 

 of the other cultures. Where there was any difference in the reaction 

 one of the normal plum strains was always used as a basis for comparison. 



Fig. 67. — Flagella of Bacterium Pruni. Stained 

 from a culture of the peach strain of the organ- 

 ism grown in bouillon 



