BACTEEIA OF THE SOIL 



69 



root. Stain the sections in 1 per cent acetic acid in which are 

 dissolved equal portions of fuchsin and methyl violet. Wash the 

 sections briefly with water and make microscopic examination. 



Fis. 30. Increased growth of beans due to inoculation with B. radicicola 



Plant on the left grown in uninoculated soil ; plant on the right grown in inoculated 

 soil. (Alter Ferguson) 



Look especially for the " infection threads " extending through 

 the cortical cells of the root. The protoplasm of the root cells 

 and tubercle cells should appear blue, and the bacteria red. 



