title: Dryadoideae
text: # Dryadoideae
  
  The subfamily Dryadoideae consists of four genera in the family Rosaceae, all of which contain representative species with root nodules that host the nitrogen-fixing bacterium Frankia. They are subshrubs, shrubs, or small trees with a base chromosome number of 9, whose fruits are either an achene or an aggregate of achenes.
  
  ## Taxonomic history
  
  The subfamily has at various times been separated as its own family (Dryadaceae), or as a tribe (Dryadeae) or subtribe (Dryadinae).
  
  