[Vol. 6 



40 



ANNALS OF THE MISSOURI BOTANICAL GARDEN 



This suspension was then heated, and approximately one- 

 half of it filtered through ordinary filter paper. 



Twenty-five-cc. portions of the filtered and of the unfiltered 

 medium were distributed into 1000-cc. "Nonsol" Erlenmeyer 

 flasks, each containing a pinch of CaCO.*. Inoculations were 

 made as described above from the same suspension and on the 

 same date. Incubation was also under the same conditions 

 and date. The results are reported in table xv. 







TABLE XV 



MODIFIED KASERER'S SOLUTION 







No. 



Treatment 



Nitrogen 

 1 (mgs.) 







Unfiltered 







Shelf 



115* 

 116* 

 117 

 118 



Check 

 Check 

 Inoc. 

 Inoc. 



. . ._. .__ ..... . .._ 



0.11 

 0.05 

 0.94 

 0.95 





Shaker 



119 



120 



Inoc. 

 Inoc. 



2.33 

 2.40 





r 



Filtered 





Shelf 



91* 

 92 

 93 

 94 



Check 

 Check 

 Inoc. 

 Inoc. 



0.07 

 0.06 

 1.15 

 1.54 



Shaker 



95 

 96 







Inoc. 

 Inoc. 



2.62 

 2.72 



* 300-cc. Erlenmeyer flasks used. 



From the above data it appears that the filtered solution is 

 fully as good as the unfiltered, and that mechanical stirring of 

 the cultures is beneficial to both media. This indicates that 

 both the filtered and the unfiltered media are poorly buffered 

 and that the mechanical action of the shaker assists in the 

 maintenance of the proper H ion concentration by hastening 

 the solution of the calcium carbonate. 



An attempt was made to conduct an experiment similar to 

 the above with filtered and unfiltered solutions containing 



Remy and Rosing 's colloidal ferric oxide, but the solution 

 cipitated completely on heating, hence the results of the 

 periment were without significance. 



