conifer vs gum tree

conifer

noun
  • A plant belonging to the order Coniferales; a cone-bearing seed plant with vascular tissue, usually a tree. 

gum tree

noun
  • A eucalyptus tree, including trees now placed in the genera Angophora and Corymbia. 

  • Hypernym: tree 

  • Sapium glandulosum, found from northern Argentina to southern Mexico 

How often have the words conifer and gum tree occurred in a corpus of books? (source: Google Ngram Viewer )