Charles B. Lipman 179 



of nitrogen. The sugars employed besides mannite were dex- 

 trose, maltose, lactose and saccharose. These were all chemi- 

 cally pure and thus the solutions when made up could only con- 

 tain traces of combined nitrogen. 



A change in the method of preparing the cultures in addition 

 to the above should also be noted here. Twenty, instead of 15, 

 grams of sugar were added to each liter of solution. The latter 

 was distributed in 50 cc. portions in 250 cc. Erlenmeyer flasks 

 each of which therefore contained 1 gram of mannite or sugar. 

 The inoculations and incubation were carried out as in the pre- 

 ceding series except that the cultures in the maltose, lactose and 

 saccharose solutions were incubated for twenty-five days instead 

 of one month as were all the others. The superior nature of the 

 tap water as compared with the distilled water was seen early in 

 the incubation period. The growth in the distilled water cultures 

 was much slighter and this was particularly noticeable in the case 

 of the molds. The results of the nitrogen determinations fol- 

 low, all arranged in one table so that the various sugars may be 

 readily compared. 



The results in Table III show clearly that every one of the 

 organisms tested possesses a power, more or less marked, of fix- 

 ing atmospheric nitrogen. In some cases that power seems to 

 be so slight indeed as to be negligible but in most cases it is very 

 distinct and definite. The next striking fact which presents itself 

 for consideration in an examination of the foregoing table is the 

 great difference in the nitrogen fixing power, of the several organ- 

 isms tested, in the different media. While mannite seems to have 

 been the most favorable source of energy for the largest number 

 of organisms tested, some of the sugars employed allowed of the 

 fixation of nitrogen by organisms which did not fix any nitrogen 

 at all in mannite solutions. 



The highest amounts of nitrogen fixed were quite considerable 

 and compare well with the amounts fixed by pure cultures of Clos- 

 tridium pastorianum and some of the less vigorous species of the 

 Azotobacter group. We find here again in the dextrose and lac- 

 tose solutions a confirmation of the work of other investigators 

 above mentioned with respect to Aspergillus niger, and in the 

 mannite solutions with respect to Penicillium glaucum. While 

 the amounts fixed are in most cases not as large in these distilled 



