chla·myd·e·ous \kləˈmidēəs\adjective Etymology: probably back-formation from achlamydeous, archichlamydeous, metachlamydeous, monochlamydeous 1.: relating to the floral envelope of a plant — used chiefly in combinations < archichlamydeous > < metachlamydeous > 2.: having a perianth — opposed to achlamydeous