Mar. 24. 1919 Ammonification of Manure in Soil 339 



tion of this pigment. The reason for this discrepancy may be in part, 

 as suggested by Jordan, because of difficulty in obtaining absolutely 

 pure chemicals; but it is undoubtedly also due to the varying behavior 

 of different varieties. It has been observed in the course of the present 

 work that two different strains may behave exactly the opposite, so far 

 as concerns their abiUty to produce fluorescence in one or the other of 

 some two media investigated. Any one strain, moreover, may vary con- 

 siderably at different times in its ability to produce fluorescence. One 

 particular strain has been studied in this laboratory which was thought 

 to be Ps. fluorescens when first obtained from soil, although not showing 

 fluorescence; but after having been cultivated for several generations 

 on a beef -extract-peptone agar containing o.i per cent of nitrate, it 

 gradually became fluorescent, and at the time of writing is one of the 

 most strongly fluorescent cultures in this laboratory. (Another sub- 

 strain of this organism, kept growing meanwhile on the same agar with- 

 out nitrate, has developed no fluorescence.) A similar phenomenon was 

 observed by Severin (45) upon cultivating a denitrifying strain in nitrate 

 broth. 



The strain used in Bright's experiments as reported in the first section 

 of this paper was always found to cause decided fluorescence on all 

 ordinary media. 



RELATION To OXYGEN. — Apparently all of the group are strictly aero- 

 bic. This is certainly true of all that have been studied here. 



IviQUEF ACTION OF GELATIN. — Typical Ps. fluorescens is a very vigorous 

 liquefier. Slow liquefiers are common, as shown by Edson and Carpen- 

 ter {13), although but few have been found in the present work. Non- 

 liquefiers have been observed occasionally in the soils investigated here. 



The gelatin colonies of fluorescent organisms vary according to the 

 rapidity of liquefaction. Typical Ps. fluorescens produces a rapidly 

 liquefying colony with entire edges that liquefies the entire plate in a 

 few days. The strain studied in this work produced a colony of this 

 type, also characterized by its clear structureless center; fluorescence 

 was sometimes present, sometimes absent. 



Ammonification. — ^Ammonia is produced" from proteid by all the 

 fluorescent organisms so far as they have been studied. Blanchiti^re 

 (/) has made a careful study of the ammonification of asparagin by a 

 fluorescent liquefier, agreeing well with the strain used in the present 

 work; and has found that it easily converts the amid nitrogen of this 

 compound into ammonia, but the aspartic nitrogen less readily. 



Action on sugars and glycerin. — Apparently no fluorescent organ- 

 ism has been recorded as producing gas from sugars or glycerin. Nearly 

 all writers have found acid to be produced from dextrose, but in regard 

 to other sugars the results are conflicting. The reason for this in part 

 is that the technic generally used is bound to give meaningless results. 

 Thus, Tanner (49) and Edson and Carpenter (rj) both determine acid 



