The Collaborative International Dictionary of English v.0.48:

Oophoridium \O`o*pho*rid"i*um\, n.; pl. L. Oophorida, E.
   Oophoridiums. [NL., dim. fr. Gr. ?. See Oophore.] (Bot.)
   The macrosporangium or case for the larger kind of spores in
   heterosporous flowerless plants.
   [1913 Webster]