What does antheridium mean?
The definition of antheridium
An`ther*id”i*um, n.; pl. Anthplwidia.
Etym: [Anther + (Bot.)

The male reproductive apparatus in the lower, consisting of a cell or other cavity in which spermatozoids are produced; — called also spermary.

— An`ther*id”i*al, a.