THE AMERICAN 



MONTHLY 



MICROSCOPICAL JOURNAL. 



Entered at the post-office as second-class matter. 



VOL, XXI. FEBRUARY, 1900, NO, 2, 



CONTENTS. 



Cultivating Water Bacteria in Moist Atmosphere 33-39 



An Interesting Object. Edwards 40-44 



Aspergillus Oryzae. Siebel, (With Frontispiece) 44-45 



Silicia Standards for Determination of Turbidity. Whipple 51-56 



BioL,OGiCA.iv Notes. — Smuts; Turnip Rot; Wilt; Disease; 

 Lactic Acid ; Nitrification ; Mineral Nutrients of Plants ; 



Plant Hairs; Yellow Coloring Matter 45-48 



MiscELLA-HEous Notes.— Cooke. Cement; Water ; Plasmodia ; 

 Fix Tentacles ; Preservatives ; Illumination ; Fluid Mounts; 



Tumors 48-51 



Scales. Soloid Stains ; Tubercle Stains ; Baker's No. i In- 

 strument ; Cement ; Mounting Algae ; Micrometers ; Nose- 



Pieces ; Illumination 56-61 



Microscopical Societies.— Quekett ; Royal 61-62 



M1CK.0SC0PICA1, ManipuIvATion. — Mosses 62 



On the Necessity of Cultivating Water Bacteria io an At- 

 mosphere Saturated With iMoisture. 



GEORGE C. WHIPPLE. 

 According to present *]^)ractice the number of bacteria 

 in a sample of water is found by mixing a certain quanti- 

 ty of the water with a certain quantity of sterilized nu- 

 trient gelatin and allowing the mixture to solidify in a 

 Petri dish. After a longer or shorter period of incuba- 

 tion at a temperature at or about 20° C.,the colonies that 

 have developed upon the gelatin are counted, and from 

 this count the number of bacteria present in the water is 

 determined. Although this method is almost universally 

 used, and although the results obtained are sometimes of 



