Oct. 8, 192 1 Blackleg Potato Tuber-Rot under Irrigation 83 



Agar stab. — Growth somewhat best at top, abundant, spreading, 

 filiform to slightly papillate. 



Gelatin stab. — Growth best at top, filiform along the line of punctm-e, 

 liquefaction, beginning on the first day at 20° C, varying in shape from 

 crateriform or funnel-shaped to saccate and broadly infundibuliform, 

 complete in 7 to 12 days. 



Nutrient broth. — Usually slight ring and slight granular pellicle in 

 young cultures, clouding moderate to strong, persistent; medium not 

 discolored, odor absent; sediment compact, granular, somewhat dirty 

 white; one strain decidedly viscid at first, but losing this character after 

 a few replatings. j-mi/ibtia Jrff-io 



MiivK. — Coagulation and extrusion of whey at 25° C, beginning on the 

 fourth day; coagulum not digested; one strain extremely viscid at first, 

 but losing its viscidity in later replatings; medium not discolored. 



Acid production in milk. — A slight increase of acidity in milk cultiu-es 

 was noticeable after 24 hours. Two series of tests were made at certain 

 intervals within the period of 20 days, two to three cultures being used 

 on each day for every strain. The average progress of the acidity of three 

 western strains was as follows : 



AGE OP REACTION IN 



CULTURE. fuller's SCALE. 



1 day ,, +12. 28 



2 days .'. .: '. +13-49 



3 days +22. 13 



5 days +28. 00 



10 days +32. 90 



20 days .,;..„ . .^,. , i: K-. +41- 12 



The average reaction of the control tubes was +11. 8 Fuller's scale. 

 Two strains received from Dr. W. J. Morse, of the Maine Agricultural 

 Experiment Station, were tested along with the western strains and gave 

 similar reactions, one ("B. sol.") showing 37.0 and the other ("IIIA") 

 40.75 acidity on the twentieth day. The cultures were grown at 22° to 

 25° C. 



Litmus milk. — ^At 22° to 25° C. bleaching was complete at the end of 

 three weeks; thorough reddening was accomplished in seven weeks. 



Gelatin colonies. — Growth rapid, form round, edge entire, lique- 

 faction saucer-shaped. 



Agar colonies. — ^Surface colonies; growth rapid, usually round, but 

 occasionally somewhat irregular, flat to slightly raised, entire to slightly 

 undulate, finely granular with an internal ring surrounded by radiate 

 striations; color pearly white, bluish opalescent by transmitted light; 

 maximum diameter of colonies after 2 days 2 mm., after 3 days 4 mm., 

 after 7 days 7 mm., after 14 days 9.5 mm. Buried colonies lens-shaped 

 to nearly spherical, edge entire, color slightly yellow under hand lens. 



Fermi's solution. — Moderate clouding in 2 -day cultures; later 

 growth becomes copious. ii^ mc*^": 



54818*— 21 8 



