SOIL FUNGI 241 



fungi in the soil and on culture media is different. 28 The first method 

 is also not without fault, since some fungi, especially those forming a 

 long mycelium, like the Mucorales, make a more extensive growth upon 

 the plate, than other fungi. Not only are the morphological characters 

 of the organisms different in the soil and on culture media, but they 

 may vary with different media. 29 The same is true of course of the 

 physiological activities of the fungi; freshly isolated organisms behave 

 differently from those kept in culture on artificial media; young cultures 

 from spores act differently from fully developed mycelium. 



Methods of cultivation of soil fungi. 30 Fungi are cultivated to facili- 

 tate the study of their morphology, their reaction to environmental 

 conditions, and their general physiology. The organisms, therefore, 

 must be first isolated from the plate and grown in pure culture. This 

 can be accomplished much more readily than in the case of algae or 

 bacteria, since fungi grow rapidly, are aerobic, produce aerial spores 

 abundantly, and can withstand comparatively large concentrations of 

 acid. 



The media for the cultivation of fungi may be designated as natural 

 and artificial. 



Among the natural media, solid substrates including soil, hay, manure, 

 fruits, bread, and branches are largely used for the growth of fungi. 

 These are either kept at an optimum moisture or are previously steri- 

 lized, then inoculated with the organism. In the case of acid media, 

 heating at 100° for 20 minutes may be sufficient for purposes of sterili- 

 zation, but in the case of soil or hay, 1^ hours at 15 pounds pressure or 

 30 minutes at 100° on seven consecutive days is required. Fruit ex- 

 tracts, as well as manure extracts, can also be used as nutrient solutions. 



In the preparation of artificial media a nitrogen source, a carbon 

 source, and minerals must be provided. Ammonium salts, nitrates 

 and organic nitrogen compounds can be used as sources of nitrogen. 31 



28 Church, M. B., and Thom, C. Mold hyphae in sugar and soil compared 

 with root hairs. Science, N. S., 54: 470-471. 1921. 



29 Brierly, W. B. Some concepts in mycology — an attempt at synthesis. 

 Trans. Brit. Mycol. Soc, 6: pt. 2. 1919. 



30 The cultivation of fungi is described in detail by O. Brefeld — Untersuch- 

 ungen auf dem Gesamtgebiete der Mykologie, H. 14: 60. 1908; Kiister, E. Kultur 

 der Microorganismen. 3d Ed., 1921; Lafar's Handb. d. tech. Mykol. 1, 1904- 

 1907; E. G. Pringsheim— Pilzkultur. Abder. Handb. Biochem. Arb. Meth. Abt. 

 XI, T. 2: 407-444. 1921; E. Pribram. Die wichtigsten Methoden beim Arbeiten 

 mit Pilzen. Ibid. XII, H. 3: 461-482. 1924. 



31 Brenner, \V. Die Stickstoffnahrung der Schimmelpilze. Centrbl. Bakt., 

 II, 40: 555-647. 1914. 



