The Collaborative International Dictionary of English v.0.48:

Florideae \Flo*rid"e*[ae]\, prop. n. pl. [NL., from L. flos,
   floris, a flower.] (Bot.)
   A subclass of alg[ae] including all the red or purplish
   seaweeds; the Rhodosperme[ae] of many authors; -- so called
   from the rosy or florid color of most of the species.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Rhodosperm \Rho"do*sperm\, n. [Gr. "ro`don the rose + spe`rma a
   seed.] (Bot.)
   Any seaweed with red spores.
   [1913 Webster]

   Note: As the name of a subclass, Rhodosperms, or
         Rhodospermeae, is synonymous with Florideae (which
         see.)
         [1913 Webster]