folium vs stipule

folium

noun
  • A leaf, especially a thin leaf or plate. 

  • A curve of the third order, consisting of two infinite branches having a common asymptote. The curve has a double point, and a leaf-shaped loop. 

  • Synonym of turnsole (“purple dye”) 

stipule

noun
  • A basal appendage of a typical leaf of a flowering plant, usually appearing paired beside the petiole although sometimes absent or highly modified. 

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