medulla vs radicle

medulla

noun
  • The internal tissue of a plant. 

  • The medulla oblongata. 

  • The soft inner part of something, especially the pith of a fruit. 

  • The inner substance of various organs and structures, especially the marrow of bones. 

radicle

noun
  • The rudimentary shoot of a plant which supports the cotyledons in the seed, and from which the root is developed downward; the root of the embryo. 

  • A rootlet. 

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