July 27, 1906.] 



SCIENCE. 



123 



over calcium chloride. After 25 days the 

 cotton in the Petri dish was sterile; the cot- 

 ton from the desiccator was a pure culture in 

 good condition, containing numberless organ- 

 isms." They also found that cultures prop- 

 erly dried and then exposed to moist air died 

 within a few days. 



The experiment with cotton in the Petri 

 dish was evidently intended as a repetition of 

 similar experiments given in Bulletin 270 in 

 which inoculated cotton placed in Petri dishes 

 became practically sterile within a few days. 

 The analytical results obtained at the two 

 laboratories were practically identical and it 

 may now be considered fairly established that 

 legume bacteria placed upon cotton according 

 to Moore's method do not survive slow drying. 

 The exact limits of the exposure which they 

 will survive remains to be established. 



It should be kept in mind that the present 

 discussion is restricted to certain packages of 

 inoculated cotton which were offered to the 

 public last season and to the methods by which 

 these packages were produced. The point 

 which should be made clear is which of the 

 portions of cotton in the experiment of Messrs. 

 Kellerman and Beckwith most nearly repre- 

 sents these packages. The eighteen cultures 

 discvissed in Bulletin 270 were purchased in 

 the market and were the product of a single 

 commercial laboratory. They were repeatedly 

 examined, six of them being tested in each of 

 five different laboratories, and were found to 

 contain extremely few or no living specimens 

 of the desired germ. Their worthlessness for 

 practical purposes was accordingly settled be- 

 yond question. Eight other packages of in- 

 oculated cotton put up by the same firm but 

 obtained through other channels were examined 

 with similar results. 



The method of preparation of these cul- 

 tures, as stated by the manager of the com- 

 pany to the writer, was to dip the rolls of 

 absorbent cotton into the culture fluid and 

 suspend them in a room until air dry. The 

 cotton was then cut into squares and shipped 

 in pasteboard boxes. Judging from the fact 

 that the germs were practically all dead in 

 the packages examined by us, either the cotton 

 dried slowly or the germs were killed by being 



exposed to moist air. The chemicals accom- 

 panying the cultures uniformly showed the 

 presence of absorbed moisture. 



Since this commercial method of preparing 

 cultures included both slow drying and ship- 

 ment in a package which exposed the cotton 

 to moist air and the germs were actually killed 

 by this treatment, it is plain that it is the 

 cotton in the Petri dish in the experiments 

 by Kellerman and Beckwith which fairly rep- 

 resents the commercial packages. 



A careful study of the facts leads to the con- 

 clusion that the criticisms justified by our 

 results with commercial cultures are equally 

 applicable to the methods of the Bureau of 

 Plant Industry up to the season of 1905 at 

 least. Until a few months since, the member 

 of the Bureau of Plant Industry then in charge 

 of the legume-bacteria investigation was also 

 in close touch with this comm^ercial company. 

 It was accordingly to be expected that the 

 methods employed in both laboratories would 

 be practically identical and any important 

 criticism against the methods employed in, 

 or the product of, one laboratory would apply 

 to the other. For this reason an examination 

 of the methods employed, and the packages of 

 inoculated cotton put out, by the Bureau of 

 Plant Industry during the past two seasons 

 is both interesting and instructive. 



The earliest official description of the 

 bureau's method of preparing the cultures on 

 cotton is given in Letters Patent No. 755,519, 

 dated March 22, 1904, and signed by G. T. 

 Moore. These state that ' absorbent cotton 

 or other equivalent material is dipped into 

 the water containing the organisms or the 

 water containing the organisms is sprinkled 

 upon the cotton or other material and the 

 same thoroughly air dried in a chamber free 

 from dust or contamination by mold.' A 

 more recent and detailed description of the 

 method is given by L. P. Sprague in a thesis 

 presented to the faculty of the University of 

 Vermont on ' The Fixation of Nitrogen by 

 Leguminous Plants,' dated May 1, 1905. Mr. 

 Sprague served as an assistant to Dr. Moore 

 in the Bureau of Plant Industry and gives the 

 following detailed description of the method 

 there employed. " Absorbent cotton of the 



