Fig. 4

Polysiphonia morrowii. Reproductive morphology of tetrasporophytes. a Aspect of the thallus; b determinate tetrasporangial branches; c detail of a determinate tetrasporangial branch in SEM; d endogenous axillary tetrasporangial branches bearing tetrasporangia (black arrowheads). Note the branching tip (white arrowhead). e detail of a tetrasporangial branch showing sharply pointed apices; white arrowheads denote trichoblasts; f tetrasporangial series of different lengths; g arrangement of mature tetrasporangia; arrowhead denotes a non-fertile segment; h shape of released tetraspores. Scale bars a = 0.5 mm; b, d, f, g and h = 100 μm; c and e = 30 μm