caryopsis vs drupe

caryopsis

noun
  • A type of fruit in which the fruit skin is stuck to the seed coat; especially the grain of a cereal. 

drupe

noun
  • a kind of fruit, with a fleshy exterior, formed from the exocarp and mesocarp, surrounding a hardened endocarp which protects the seed. 

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