Morphology and reproduction of Bostrychia pinnata (Rhodomelaceae, Ceramiales) in laboratory culture

In unialgal culture, isolates of vegetative plants of Bostrychia pinnata often developed tetrasporangial stichidia and released viable tetraspores. Most tetra‐sporelings developed normal branching before reproduction, however, some sporelings developed procarps, and later, spermatangia on juvenille unbranched stages (< 1 mm). Most normally branched gametophytes (> 2 mm) were initially female before becoming bisexual when older and larger (> 5 mm). Unisexual male gametophytes were not seen in culture. Carposporophytes developed slowly (40–70 days) and were sometimes abortive or produced reduced numbers of carpo‐sporangia (10–15 in cultures compared with 40–50 in field material). Carpospores germinated more slowly than tetraspores and the tetrasporophytes required up to 6 months to reach reproductive maturity. The Polysi‐phonia‐type life‐history was completed in 9–12 months in the laboratory. Peripherohaptera were absent in cultured plants. The isolates from Florida, Guatemala and Peru did not reproduce sexually, but regularly underwent lower branch abscission as a means of vegetative reproduction. After several years in culture, most individual isolates became self‐incompatible. In the female, 1 or 2 procarps formed on each axial segment and most were 4‐celled with a few having 3 cells. A single branched sterile group of 3–7 cells was also present. After fertilization, the diploid nucleus in the carpogonium divided twice, isolating the capping element and trichogyne and establishing the connecting element adjacent to the auxiliary cell. In mature normal cystocarps the sterile group persisted and secreted mucilage into the central cavity. The mature pericarp was four layers thick (one layer of axial filaments and three cortical cell layers). Pseudocystocarps were common, produced no carpo‐sporangia, contained elongate sterile cells, and were enclosed with a partially developed pericarp. Carpogonia in which 4 nuclei were usually seen may indicate developmental failure resulting in pseudocystocarps.