464 BOTANICAL GAZETTE [JUNE 
nitrogen and of carbon for the mucors. The mass of detail is too great and 
too diverse to permit of recapitulation; the main features of the results, how- 
ever, may be briefly summarized. The 23 mucors studied fall into two clearly 
separated groups with respect to their ability to assimilate nitrogen from 
nitrates and nitrites. In relation to these compounds it is interesting to note 
that all forms which were capable of assimilating nitrates were also capable 
of assimilating nitrites. As with other plants, the nitrates are reduced to 
nitrites and these to ammonia in the process of assimilation. All forms grew 
well when nitrogen was supplied in the form of ammonium salts. On urea, 
18 species thrived, but Mucor Romannianus failed. In cultures with urea, 
ammonium carbonate is formed. Acetamide is not utilized. Uric acid is only 
slightly soluble, but gives good growth. The amino-acids have little nutrient 
value when they are the sole source of both carbon and nitrogen. When 
carbon is supplied in the form of glucose, the amino-acids, especially leucine 
and tyrosine, are utilized as a source of nitrogen by many of the soil mucors. 
In all cases ammonia accumulates in the culture medium. Of the non-nitroge- 
nous carbon compounds, mannite and glycerin are not used when ammonium 
sulphate is the only source of nitrogen; with potassium nitrate, however, these 
polyatomic alcohols are assimilated by 3 or 4 species. With the exception of 
reducing sugar in the culture fluid. The species which thrive on saccharose 
are unable to utilize that sugar when amino-acids serve as the only source 
of nitrogen. In explanation the author suggests that the action of the inver- 
tase of the fungi is inhibited by the presence of ammonia split off from the 
amino-acids. Starch in general seems not to be utilized, a fact which is all the 
more interesting since the conversion of starch into glucose by some species of 
izopus is the basis of a commercial process. Few species grow on inulin and 
pectin, but some on xylan and cellulose. Of the glucosides, helicin and salicin 
were tried. Helicin proved valueless, while a number of mucors were capable 
of utilizing salicin, but only to a limited extent because of the toxic properties 
of the decomposition products formed. 
These results on the whole seem to indicate that most of the common 
substances which reach the soil from the plant are only poorly suited for the 
nutrition of a group constituting, according to these investigations with the 
exception of the bacteria, one of the most abundantly represented classes of 
soil-organisms. It would be an interesting problem to determine to what extent 
the nutrition of soil mucors is dependent upon decomposition of plant products 
brought about by bacteria and other soil organisms. 
In a third paper,’ which forms the conclusion of HAGEm’s investigations of 
Norwegian mucors, the author gives critical notes on their nutrition. Mucor 
8Hacem, O., Neue ooaeasew iiber norwegische Mucorineen. Ann. 
Myc. nialeien: figs. II. 1910 
