The life history of Desmarestia firma (C. Ag.) Skottsb. (Phaeophyceae, Desmarestiales)

The life history of the South African species Desmarestia firma (C. Ag.) Skottsb. is described from culture. Zoospores from unilocular sporangia give rise to separate filamentous male and female gametophytes. Male gametophytes bear flask-shaped antheridia, each containing a single antherozoid. Female gametophytes, more robust and darkly pigmented than the males, bear club-shaped oogonia, each producing one or possibly more eggs. Trichothallic sporophytes are firmly fused to the female gametophytes. Specimens were cultured to a stage where they produced rhizoids and cortication became apparent. These findings disagree with suggestions that the gametophytes of oppositely branched species of Desmarestia are monoecious.