UNUSUAL PHENOMENA IN THE LIFE HISTORIES OF FLORIDEAE IN CULTURE1

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Abstract
Several Florideae grown in natural seawater media under defined laboratory conditions have interesting and unusual life histories. Antithamnion occidentale males of one generation produced tetraspores that gave rise to nonsporangiate males. The functional females of A. pygmaeum developed spermatangia and tetrasporangia; the tetraspores formed new females. Antithamnion defectum tetrasporophytes of one generation bore spermatangia in addition to tetrasporangia; the tetraspores gave rise to typical gametophytes. Tetraspores from successive generations of Callitham‐nion sp. developed into tetrasporophytes and males but no females were produced. Functional female gametophytes of Platythamnion sp. bore abortive tetrasporangia. Field‐collected plants of two species of Fauchea produced tetraspores that yielded additional sporangiate plants: those of F. pygmaea being bispo‐rangiate and tetrasporangiate, and those of F. lacini‐ata being strictly tetrasporangiate. Male plants of Pleonosporium vancouverianum from a running seawater table bore spermatangia and polysporangia when collected. The same plants in unialgal culture produced only spermatangia.