Pyxidium
Pyxidium , noun
[New Latin, from Greek {not transcribed}, dim. a {not transcribed} a box. See Pyx.]
(a)
(Botany) A pod which divides circularly into an upper and lower half, of which the former acts as a kind of lid, as in the pimpernel and purslane.
(b)
(Botany) The theca of mosses.