PLATE 12. 



NITROGEN-FIXING BACTERIA in situ IN NODULE ON ROOTLET OF PEA. 

 X 400. 



N"lTROGEN-FlXING BACTERIA in SttU IN ROOT-NODULE 



OF PEA. (Section of Nodule), x 500. 



NITROGEN-FIXING BACTERIA in situ IN ROOT-NODULE 

 OF PEA. (Section of Nodule), x 600. 



[To face page 134. 



