THE DECOMPOSITION OF CELLULOSE IN SOILS 441 



etc. Of the thirty-four species which grow upon gelatin, nineteen Hquefy 

 the gelatin. Many forms produce a growth upon beef agar and potato 

 agar slopes in 24 hours. A few species grow quite luxuriantly upon 

 potato cylinders, but in most cases no growth or only a scant growth is 

 produced, even when the cultures are held in a moist chamber for 30 

 days. Twenty-nine species produce an acid reaction and three an alkaline 

 reaction in litmus milk. Four species do not change the reaction of lit- 

 mus milk. The milk is coagulated or digested by only six species. 



The destruction of cellulose can be secured in nutrient solutions con- 

 taining ammonium sulphate, potassium nitrate, peptone, casein, or aspar- 

 agin as the source of nitrogen. Peptone appears to give the best results 

 for the largest number of organisms, while casein is least satisfactory 

 for many forms. No destruction of cellulose has been secured without 

 the addition of combined nitrogen to the nutrient solution. This would 

 seem to indicate that the cellulose-dissolving organisms do not draw 

 freely upon the free nitrogen of the air for their nitrogen supply. This 

 hypothesis is further strengthened by the behavior of the organisms in 

 dextrose solutions. When dextrose is added to nutrient solutions con- 

 taining combined nitrogen, many of the cellulose-dissolving organisms 

 vigorously attack the dextrose ; but when the nutrient solution is care- 

 fully freed from combined nitrogen the dextrose is attacked very slowly 

 and little or no fixation of nitrogen is secured. 



No gas is formed by any of the species in cellulose or other carbo- 

 hydrate broths. The quantity of acid produced in carbohydrate broths is 

 fairly constant for the species, but quite variable for different species. 

 With dextrose, lactose, maltose, saccharose, and starch the quantity of 

 acid produced in 12 days at 30° C. usually lies between 1 and 2 per cent 

 on Fuller's Scale. The amount of acidity in the mannite and glycerine 

 solutions is very generally less than 1 per cent, and in many cases no 

 acidity is produced in these solutions. Two species cause no change in 

 the reaction of any of the carbohydrate broths. B. rossicus gave an alka- 

 line reaction in all the broths, while Ps. effusa gave an alkaline reaction 

 in the lactose and saccharose broths. The alkaline reaction is probably 

 due to the formation of ammonia from the peptone in the solution, the 

 ammonia produced being more than sufficient to neutralize any acid 

 formed. In Dunham's solution fourteen species produce ammonia, while 

 twenty forms produce a compoimd which gives typical reactions for ni- 

 trites with the Griess' reagent and also with the starch-iodide and the 

 diphenylamine solutions. There seems to be no reason for concluding 

 that the substance is not nitrite except that nitrite formation has been 

 thought to be restricted to a particular group of organisms which do not 

 grow upon ordinary media. The quantity of nitrite formed by the 

 cellulose-dissolving forms is small ; in most instances not more than one 



