Peltasta australis J. Agardh (1892 , p. 102)

Peltasta australis J. Agardh (1892, p. 102)

Thalli are recorded from West Island, South Australia, to Western Port (Phillip Island), Victoria and the east coast of Tasmania ( Kraft and Womersley 1994, p. 327). Fronds are erect on rocky substrata and narrowly linear, complanate, compressed and dichotomously branched ( Fig. 1 d View Fig , 5 a View Fig ). Anchorage is by a series of short basal stolons and haptera ( Fig. 1 e View Fig ). Axes are bluntly rounded and slightly flared at the multiaxial tips, and mature cross- and long-sections ( Fig. 2 c View Fig ) consist of a narrow core of deeply pigmented filaments surrounded by a wide expanse of colorless, subisodiametric cells ( Fig. 2 c View Fig ) bordered on both sides by a cortex of ovoid surface cells subtended by a single layer of small isodiametric cells ( Fig. 2 d View Fig ). Tetrasporangia are basally pit-connected to cells of the subsurface layer and mostly accompanied by a single elongate companion cell ( Fig. 3 g View Fig ). Male gametes form in subsurface ampullae and consist of elongate spermatangia that are released through surface pores in the colorless cuticle ( Fig. 3 h View Fig ). The monoecious gametophytes ( Fig. 5 a View Fig ) initiate cystocarps in subapical swellings ( Fig. 5 b View Fig ) and produce carposporophytes within globular, ostiolate pericarps at maturity ( Fig. 5 c View Fig ). Carpogonial branches are three-celled ( Fig. 5 d View Fig ; Kraft 1977 b, fig. 6G) and form deep in the cortex on supporting cells that subtend slightly swollen auxiliary cells ( Fig. 5 d View Fig ) with which the presumably fertilised carpogonia directly fuse ( Fig. 5 d View Fig , central arrow). Vegetative cells to the interior of the extended cortex housing the carpogonial branches become frequently linked to adjacent cells by direct fusions ( Fig. 5 d View Fig ) even prior to zygote formation. The presumably diploidised auxiliary cell links up and fuses with cells of adjacent vegetative filaments, and issues numerous gonimoblast initials and filaments circumferentially ( Fig. 5 e, f View Fig ). As the carposporophytes placentate ( Fig. 5 g, h View Fig ), an ostiole progressively differentiates from the surface and extends deeply downwardly to the gonimoblasts ( Fig. 5 g View Fig ). The ultimate development of gonimoblasts on the central placental core consists of dense arrays of long, parallel files of elongate cells ( Fig. 5 i View Fig ) that bud off spherical carposporangia and contain varying numbers of knotted cells ( Fig. 5 j View Fig ) that appear to be islands of arrested growth.