perigone vs velum

perigone

noun
  • A sac surrounding the generative bodies in the gonophore of a hydroid. 

  • perianth 

  • In mosses, the involucral bracts of a male flower. 

velum

noun
  • a delicate membrane found on certain protists 

  • a veil-like membrane of immature mushrooms extending from the margin of the cap to the stem and is torn by growth, to reveal the gills 

  • a locomotory and feeding organ provided with cilia found in the larval stage of bivalves 

  • a thin membrane partially covering the cluster of sporangia near the leaf base in quillworts and their extinct relatives 

  • the soft palate 

  • a annular membrane, typically bordering a cavity, especially in certain molluscs, medusae, and other invertebrates 

  • an accessory cloud resembling a veil extending over a large distance; normally associated with cumulus and cumulonimbus 

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