Back-crossing 



The mating or crossing of a hybrid with either one of 

 its parents or parental stocks. 



Back-fire 



A fire started purposely ahead of an advancing fire to 

 remove inflammable material and thus control the main fire. 



Backftash 



The movement of a poison through root grafts from 

 trees that have been treated with poison to non-treated trees. 



Bacteriophage 



A virus which destroys bacteria. 



Bacteriorhizae 



The nodules on the roots of most legumes and on some 

 other plants such as alders which contain bacteria that can 

 use atmospheric nitrogen in synthesizing organic compounds. 



Badlands 



Areas of rough, irregular, eroded land on which most of 

 the surface is occupied by ridges, gullies, and deep channels, 

 with sparse vegetation. 



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