440 SOIL SCIENCE 



1. Grind a quantity of the dry plant substance to a flour and sift 

 through bolting cloth to remove all coarse material. 



2. Boil 50 gm. of the sifted flour in a 2 per cent potassium hydrate 

 solution for one-half hour; pour into a large bottle or carboy and wash 

 through repeated changes of water until free from potassium. 



3. Expose the washed material to the action of chlorine at ordinary 

 temperatures for one-half hour. Wash as before imtil the chlorine is re- 

 moved. 



4. Subject to a second alkaline hydrolysis by boiling with 2 per cent 

 caustic soda for one-half hour. Wash until the solution is no longer al- 

 kaline. I -^-'i^ 



The cellulose is thus isolated in a very pure state, and if the grinding 

 of the plant material has been sufficiently fine, the finely divided cellulose 

 prepared in this way is quite as satisfactory for the preparation of cellu- 

 lose agar as that prepared from filter paper by tlie ordinary method. 



In the present work it has not been possible to make an extensive 

 study of the decomposition of the celluloses in different plant substances. 

 However, it has been demonstrated that the cellulose-dissolving bacteria 

 isolated from soils by means of the cellulose agar plate method, have the 

 power of dissolving the cellulose of alfalfa. Twenty-five species of cellu- 

 lose-dissolving bacteria were plated to cellulose agar containing pure 

 cellulose from the alfalfa plant and in every instance the cellulose was 

 dissolved as readily as that prepared from filter paper by the ordinary 

 method. 



Discussion of General Characteristics of Cellulose-Dissolving 



Bacteria 



The author's exhaustive studies of a large number of soils from widely 

 separated regions have shown that there are numerous species of bacteria 

 which have the power to destroy cellulose. All of the forms studied are 

 rod-shaped organisms varying in length from .8 to 3.50 fi. Involution 

 forms have been observed for only three species. Five species have been 

 found to produce spores. Twenty-seven of the thirty-six species isolated 

 are motile. The arrangement of the flagella on the motile forms shows that 

 seven species belong to the genus Pseudomonas and twenty to the genus 

 Bacillus. All species stain readily with the aniline dyes. All are facul- 

 tative in nature, but invariably develop most rapidly imder aerobic con- 

 ditions. With some species, the development under anaerobic conditions 

 is very slow. All species grow well from 20° to 37.5° C, and some 

 forms have been found to develop at temperatures as high as 45° C, but 

 much more slowly than at the lower temperatures. The optimum tem- 

 perature for most species seems to lie between 28° to 33° C. 



With two exceptions, the cellulose-destroying bacteria form more or 

 less growth upon ordinary culture media such as beef gelatin, beef agar, 



