INFLUENCE OF ENVIRONMENTAL CONDITIONS 779 



York has been made by Barthel, 33 who found, in addition to various 

 aerobic and anaerobic, spore-forming and non-spore forming bacteria, 

 also actinomyces and fungi (Mucors, Torulae) . Nitrifying bacteria were 

 present only in three out of fourteen soils of Disko, while Azotobacter 

 was absent in all; Bac. amylobacter could not be demonstrated, although 

 its presence originally was not excluded; Azotobacter and protozoa 

 were found in the Greenland soils. 



Various investigations have been made concerning the temperature re- 

 lations of fungi, especially in relation to fruit rot in storage. The great 

 majority of these fungi grow at 4.5°C. and even develop slowly at 

 0°C. 34 The minimum temperatures of germination of fungi vary from 

 1°C, for Monilia fructigena and Pen. digitatum, to 6° to 9° for Cephalo- 

 thecium roseum. Zb Spores of Alternaria, Botrytis, Pen. expansum and 

 Sclerotinia germinate slowly at zero; the spores of Ceph. roseum, Fu- 

 sarium radicicola and others failed to germinate at zero but germinated 

 slowly at 5°C. 36 Some fungi, like Pen. expansum, after starting growth 

 at ordinary temperatures, were able to continue growth at zero. The 

 rate of growth increases with rise in temperature up to a certain limit, 

 being a direct function of (t — t°) , where t is the particular temperature 

 and t° is the minimum temperature. 37 



It is of interest to call attention, in this connection, to the changes 

 in the numbers and activities of microorganisms in the soil with the 

 season of the year, due to changes in soil temperature and moisture, 

 and introduction of available organic matter, soil aeration, etc. Rus- 

 sell and Appleyard 38 found that there is very little activity in the soil 

 during the winter months (November to March). Below 5°C, the 

 changes taking place in the soil are very slow; above that temperature, 

 bacterial numbers, C0 2 production, and nitrate accumulation all 



33 Barthel, 1922 (p. 149). 



34 Schneider-Orelli, O. Versuche iiber die Wachstumsbedingungen und 

 Verbreitung der Faulnispilze des Lagerobstes. Centrbl. Bakt. II, 32: 161-169. 

 1912. 



" Ames, A. The temperature relations of some fungi causing storage rots. 

 Phytopathol., 11: 19. 1915. 



38 Brooks, C, and Cooley, J. S. Temperature relations of apple-rot fungi. 

 Jour. Agr. Res., 8: 139-164. 1917. 



37 Brown, W. On the germination and growth of fungi at various temperatures 

 and in various concentrations of oxygen and of carbon dioxide. Ann. Bot., 36: 

 257-283. 1922. 



38 Russell, E. J., and Appleyard, A. The influence of soil conditions on the 

 decomposition of organic matter in the soil. Jour. Agr. Sci., 8: 385-417. 1917. 



