MiCRO-OFGANiSMS 0* M ah.k S.\r ."'"7 



6 davs drying. In one of the 5 tests made no growth was ob 

 tained in a tube inoculated with a cover slip dried for <> days. 

 Growth occurred 2 days after inoculation with cover slips dried 

 for i) days. No growth occurred in tubes inoculated with covel 

 slips dried for 20 days. Tubes were held under observation for 

 10 days after the cover slips were introduced. 



Insolation. — Agar plates were sown with such dilutions as 

 to produce from 100 to 200 colonies, and allowed to stand until 

 thoroughly hardened. One-half of the plate was covered with 

 an opaque screen, and the cultures exposed on ice to the influence 

 of direct sunlight for 15 minutes. The exposure was made in 

 the middle of the day on August 28. After exi><>sure the plates 

 were returned to the incubator and allowed to remain at a 

 temperature of 25 for 3 days. The colonies were then counted 

 upon exposed and unexposed portions of the plate, with re- 

 sults as follows: 



Unexposed side 

 117 colonies 

 85 " 

 80 " 

 27 " 

 50 " 

 85 " 

 40 " 



484 " 

 Calculated percent killed, 46.7 



Production of alcohol. — Four different media were em 

 ployed in the determination of alcohol production, viz.: 2'', 

 dextrose bouillon, 2% sucrose bouillon, potato broth, and maple 

 sap. Inoculation was made in liter flasks in 500 cc. portions of 

 media to which 10 gr. of calcium carbonate had been added im- 

 mediately before sterilization. The cultures were held at room 

 temperature, 20 to 24 C. After 10 days incubation the undis- 

 solved calcium carbonate was removed by filtration, the cultures 

 made slisrhtlv acid with hvdrochloric acid and then distinctly 

 alkaline with sodium carbonate, the precipitated calcium car- 



