480 SOIL SCIENCE 



a dilute hydrochloric acid solution, prepared by adding one part of con- 

 centrated acid to twenty parts of water. 



3. Cellulose agar can be prepared from the cellulose in plant tissues 

 by grinding the dry plant substances to a flour and isolating the cellu- 

 lose in a pure state from the finely ground substance. Cellulose prepared 

 in this way is quite as satisfactory for the preparation of cellulose agar as 

 that prepared from filter paper in the ordinary way. 



4. Twenty-five species of cellulose-dissolving bacteria have been 

 grown on culture media containing cellulose prepared from alfalfa flour. 

 All of the organisms plated to this medium dissolved the cellulose as 

 readily as that prepared from filter paper. 



5. All of the cellulose-dissolving organisms studied develop most 

 rapidly in the presence of air, although more or less growth can be secured 

 under anaerobic conditions. 



6. Most of the cellulose-destroying bacteria grow well upon ordinary 

 culture media. A few forms do not grow upon ordinary culture media, 

 but only upon media containing cellulose. 



7. The cellulose-dissolving bacteria assimilate nitrogen from organic 

 as well as inorganic nitrogenous compounds. Many forms destroy cellu- 

 lose rapidly when the culture medium contains nitrogen in the form of 

 peptone, ammonium sulphate, potassium nitrate or casein. Peptone ap- 

 pears to be most favorable for the largest number of species, while casein 

 is usually least favorable of the nitrogen compounds tested. 



8. The quantity of acid formed in carbohydrate broths, in 12 days at 

 30*^ C. usually amounts to from 1 to 2 per cent on Fuller's scale, with 

 dextrose, lactose, maltose, saccharose, and starch. The per cent of acid- 

 ity in mannite and glycerine solutions is usually less than 1 per cent and in 

 many instances no acid is formed from these substances. 



9. Many species of cellulose-dissolving bacteria produce a small 

 quantity of nitrite in Dunham's solution. The nitrite is presumably 

 formed from the peptone. A starch nitrate broth free from peptone has 

 therefore been used instead of the standard nitrate broth for determining 

 the nitrate reducing power of these organisms. 



10. Filamentous fungi play a much more important role in the de- 

 struction of cellulose in the humid soils of the eastern part of the United 

 States than in the semi-arid soils of southern California. 



11. Species of cellulose-dissolving Actinomyces have a wide distri- 

 bution in soils and are unquestionably a factor in the destruction of 

 cellulose in nature, 



12. The very rapid destruction of cellulose which occurs in many 

 soils of southern California is probably due to favorable climatic and cul- 

 tural conditions which make possible the rapid development of the cellu- 

 lose-dissolving organisms rather than to the unusually active nature of 

 the cellulose-dissolving soil flora. 



