170 DecoiHjtoslfioii of Celhdosr 



but further work is required before the chemical character of the mucilage 

 can be definitely established. As far as soil conditions are concerned, it 

 is not improbable that an extensive production of mucilage from plant 

 residues would exert some action on the physical behaviour of the soil; 

 from the chemical standpoint, and on account of its insolubility in acids 

 and solubility in ammonia, the mucilage would, without doubt, appear 

 in the "crude humus" fraction in the conventional soil analysis. 



The Relation of Cellulose-decomposing Organisms to 

 Nitrogen Fixation. 



Since this, and a preceding investigation on nitrogen fixation, arose 

 from the necessity of accounting for the observed gains in nitrogen in 

 soils that had been allowed to revert to prairie conditions, we may be 

 permitted to refer briefly to the relation between cellulose, as distinct 

 from crude plant residues, and the assimilation of atmospheric nitrogen. 

 In the first instance it was supposed that although cellulose is not 

 directly available to such nitrogen-fixing organisms as Azotobacter, the 

 products of decomposition would include sugars such as are formed on 

 the hydrolysis of cellulose by acids, and that these compounds would 

 serve as sources of energy for Azotobacter. It has already been seen, 

 however, that the formation of sugars during decomposition is highly 

 problematical, but that there are indications of the formation of volatile 

 fatty acids, and the value of some of these for nitrogen-fixation has 

 frequently been observed^. Moreover, there is definite evidence that 

 the cellulose breakdown products do increase nitrogen-fixation and in 

 this connection the following results are submitted. 



Two sets, each of six flat bottomed flasks, were prepared; one set 

 (A) received 50 c.c. of mineral salt solution containing 0-1 per cent, 

 mannite and, in addition, 1-0 grm. each of cellulose and calcium carbo- 

 nate. The second set (B) received the same additions with the exception 

 that in this case the mannite was replaced by a supply of sodium nitrate 

 equal to 0-010 per cent, nitrogen, the main object of this variation 

 being to ascertain whether the associative action could be initiated 

 equally well by nitrogen-fixation (set A) or cellulose decomposition 

 (set B). From the results given below it will be seen that this was not 

 the case and set B actually lost nitrogen — possibly by the action of such 

 denitrifying cellulose-decomposing bacteria as were observed by van 

 Iterson^. 



I Mockeridge, F. A., Biochcm. J. llll.-j, 9, 272-283. 

 - Iterson. C. van, loc. cil. 690. 



