174 



SCIENCE 



[N. S. Vol. XL VI. No. 1182 



is set free and may be subsequently nitrified 

 for use by the higher plants. Various fertil- 

 izing materials containing complex nitrog- 

 enous compounds may be ammonified by 

 soil fungi, and their decomposition consid- 

 erably facilitated. For instance, experi- 

 ments with cyanamide show its rapid trans- 

 formation to ammonia by certain molds. 

 Ammonia production from urea by molds 

 has also been definitely proven. 



The non-nitrogenous portion of the soil 

 organic matter is also attacked by many 

 molds. Thus experiments have shown that 

 cellulose is rapidly decomposed by many 

 species, and other substances such as sugars, 

 pectins, oils, fats, waxes, organic acids, etc., 

 are likewise broken down by molds. Some 

 recent results secured in our laboratories 

 show the large carbon-dioxide production 

 by molds. No doubt, therefore, remains but 

 that these organisms play an extremely im- 

 portant part in the decomposition of all soil 

 organic matter and indeed certain results 

 indicate that their action along this line 

 may be much greater than that of bacteria, 

 at least under certain soil conditions. 



No experiments have yet been reported 

 which indicate that molds may bring about 

 nitrification, and this process, therefore, 

 still appears to be purely bacteriological. 

 Further experiments may modify this con- 

 clusion. 



Denitrification and deazotofieation, how- 

 ever, processes now known to be of slight 

 significance in normal soils, but which may 

 occur in highly manured, specially treated 

 greenhouse and market garden soils, may 

 possibly be brought about by the action of 

 molds. The introduction of these organ- 

 isms with the manure used may be an im- 

 portant factor here. Definite data along 

 this line are lacking at the present time. 



Non-symbiotic nitrogen fixation, or azofi- 

 cation by molds has been studied from time 

 to time and indications have been secured 



that certain species may be able to utilize 

 the nitrogen of the atmosphere. The re- 

 sults, as a whole, however, are far from sat- 

 isfactory and indeed the conclusion has 

 been drawn that at the present time the 

 "weight of the conclusions on the fijxation 

 of nitrogen by fungi seems to be on the 

 negative side." Further experiments 

 along this line are certainly desirable. 



The utilization of various nitrogen com- 

 pounds by molds has been studied to some 

 extent, and it has been found that ammonia 

 and nitrate compounds are assimilated by 

 these organisms in considerable amounts. 

 Thus under extreme conditions of mold 

 growth it is conceivable that molds may be 

 actual competitors with the higher plants 

 for nitrogenous food materials. It is not be- 

 lieved, however, that such conditions would 

 occur except very rarely. A knowledge of 

 mold growth in soils may be of some signifi- 

 cance, nevertheless, in connection with the 

 questions involved in the fertilization of 

 soils with nitrates and ammonium salts. 



The decomposition of mineral compounds 

 in soils by molds has been studied only to 

 a very slight extent. Data secured in our 

 laboratories very largely in connection with 

 certain chemical and bacteriological stud- 

 ies indicate, however, that these organisms 

 may play an extremely important role, not 

 only in preparing nitrogenous food mate- 

 rials for plants as has been indicated, but 

 also in making other mineral constituents 

 available. Complete data along the various 

 lines indicated will be published later. 



Studies of the production of available 

 phosphorus by bacteria and molds have 

 shown the vigorous action of various fungi 

 in this direction. Several experiments car- 

 ried out by various methods have shown 

 that rock phosphate is apparently trans- 

 formed much more rapidly into a soluble 

 form by many molds than by bacteria. The 

 importance of further stud}'' along this line 



