Webster’s Revised Unabridged Dictionary · 1913
Pyxidium
Pyx·id′i·um, n.; pl. Pyxidia (#). [NL., fr. Gr. ?, dim. a ? a box. See Pyx.] (Bot.) (a) 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) The theca of mosses.