56 LABORATORY BACTEUIOLOGY. 



GROUP VI. SYMBIOTIC NITROGEN FIXATION. 

 Exercises XLIV. to XLVI. 



BXEECISE XLIV. 



THE ISOLATION AND EXAMINATION OF B. EADICICOLA FROM 



DIFFERENT LEGUMES. 



1. Thoroughly wash the roots of several legumes (e. g., 

 red clover, alfalfa, sweet clover, cowpeas, etc.), under the 

 tap. 



3. Compare the size, numbers and location of the nodules 

 on the roots of these different legumes. 



3. Eemove the nodules from each, wash under the tap and 

 immerse for 3 minutes in mercuric chloride solution 

 (1:500). 



4. With flamed forceps remove the nodules and take up 

 the excess of the solution between the folds of filter paper 

 wrung out of the same solution. 



5. Then each nodule is held in flamed and cooled forceps 

 and an incision made in it by means of a sterile knife or a 

 chisel-edged platinum needle. 



6. A sterile platinum needle is thrust into the opened 

 nodule and rotated gently to cause some of the crushed tissue 

 to adhere to it. 



7. Then tubes of sterile "Eadieicola" solution are inocu- 

 lated. 



