148 CROWN-GALL OF PLANTS. 



This experiment was repeated in October, 1910, with the same 

 result: In 48 hoiu's, no reaction either cold or on heating, growth 

 good in form of shreds and strings; 83 hours, no reaction cold; on 

 heating 5 minutes at 80° C, doubtful or possibly a trace of pink. 

 The test was made in both 1 and 2 per cent peptone water. 



REDUCTION OF NITRATES. 

 PRELIMINARY STATEMENT. 



As already pointed out, the daisy organism does not reduce 

 nitrates. 



It is probable also that none of the others reduce nitrates, in the 

 ordinary meaning of the term, but some doubt still exists. 



Early tests by the junior writer having led to contradictory results 

 (in some instances), further experiments were made in 1910, but not 

 enough wholly to clear up the situation. The following is a summary 

 of all our experiments: 



DAISY. 



(1) Several old tests hy Doctor Smith — -all negative. 



Old tests hy Miss Brown. — (2) 13 days, negative; (3) 5 days, both 

 old and newest strains, negative; (4) 33 days, negative. 



Tests in 1910 hy Doctor Smith. — (5) 69-day-old cultures by Miss 

 Brown in her nitrate bouillon No. 600. Old daisy, 2 tubes (strongly 

 alkaline to litmus): Trace of blue in bottom which disappears on 

 shaking; reagents pure, i. e,, tested. Newest daisy: Trace of blue 

 in bottom which shakes out. The checks also give a purple reaction 

 in bottom of tube but not if the starch is withheld. The starch was 

 then suspected and retested, but on adding KI water and II2SO4 to 

 20 c. c. of the boiled starch no blue reaction whatever was obtained. 



PEACH, 



Old tests hy Miss Brown. — (1) 13 days, reduced; (2) 5 days, slight 

 reduction; (3) 33 days, reduced. 



Tests in 1910 hy Doctor Smith. — (4) 69-day-old culture by Miss 

 Brown in her bouillon No. 600 (culture strongly alkaline to litmus), 

 copious reduction; does not shake out; check tubes give some blue 

 reaction at bottom which goes on shaking; reagents pure, (5) 

 Plates poured and portions of 8 colonies transferred to 8 tubes of 

 bouillon; strong growth. Tested after 7 days, all negative, i. e,, 4 

 failed, and 4 showed traces of blue at bottom in the bacterial pre- 

 cipitate, which color disappeared on shaking. Check tubes showed 

 no nitrite present. The cultures were then tested for nitrate 

 (H2SO4 and diphenylamine) with customary blue reaction, (6) Sec- 



213 



