Definition of mesosporium in US English:

mesosporium

noun

Mycology Botany
  • The middle layer of the wall of any of several types of three-layered spores, especially of the ascospore of a fungus.

Origin

Late 19th century; earliest use found in Mordecai Cooke (1825–1914), naturalist and mycologist. From meso- + -sporium.

Pronunciation

mesosporium

/ˌmɛsə(ʊ)ˈspɔːrɪəm/