1915] 



C. H. Crabill and H. S. Reed 



31 



shown by this Petri dish method, because the process of chemical 

 reduction is usually counteracted by rapid oxidation of the products 

 in contact with atmospheric oxygen. 



For a number of the experiments a stock agar was prepared 

 according to the following formula, filtered, and steriHzed in the 

 autoclave: Distilled water, 1000 c.c. ; magnesium sulfate, 0.5 gm.; 

 di-potassium hydrogen phosphate, i.o gm.; potassium chlorid, 

 0.5 gm.; ferroiis sulfate, o.oi gm.; agar, 20.0 gm. This stock 

 medium is sHghtly acid in reaction. It presents no carbon-containing 

 nutrient and consequently does not support microorganic growth. 

 To this various zymolytes in the form of carbon containing Com- 

 pounds are added and inoculated with the organisms whose activities 

 are to be tested. 



TABLE I 



Data pertaining to amylolytic tests on starch-agar. 



Organism 



Glomerella rufomaculans . . . 

 Spharostilbe coccophila. . . . 



Pseudopeziza ribis 



Helminthosporium turcicum 



Alternaria sp 



Phyllosticta pirina 



Septoria lycopersici 



Aspergillus niger 



Oospora Scabies 



Streptothrix sp 



Diplococcus sp 



Micrococcus citricus 



B. fluorescens liquifaciens . . 



B. pyocyaneous 



B. cerogenes 



B. denitrificans 



Bad. tumefaciens . 



B. coli 



Bact. lactis acidi 



B. mycoides 



B. prodigiosus 



B. vulgaris 



B. putidum 



B. hartlebii 



B. butyricus 



B. campestris 



Growth 



Starch dissolution 

 beneath centre 



Halo produced 



Good 



Poor 

 Good 



None 

 Good 



Fair 

 Slight 



Fair 

 Good 



Weak 

 Good 



Good 



Slight 



None 



Weak 



Excellent 



None 



None 



Amylase. The action of this enz)rme may be conveniently 

 demonstrated by cultivating organisms on starch-agar, made by 

 adding to 500 c.c. of the melted stock agar, 10 gm. of corn starch 



