cotyledon vs ovule

cotyledon

noun
  • The leaf of the embryo of a seed-bearing plant; after germination it becomes the first leaves of the seedling. 

  • Each of the patches of villi on the foetal chorion in the placenta of ruminants and some other mammals. 

ovule

noun
  • The structure in a plant that develops into a seed after fertilization; the megasporangium of a seed plant with its enclosing integuments. 

  • An immature ovum in mammals. 

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