Reptataxis rhizophora (A.H.S.Lucas) Kraft (1977 b , p. 241)

Reptataxis rhizophora (A.H.S.Lucas) Kraft (1977 b, p. 241)

This genus is knonw to be endemic to Lord Howe Island that lies at the southern limit of consolidated coral-reef formation in the Tasman Sea approximately one-third of the way between the east coast of Australia and New Zealand. Thalli consist of narrow, cartilaginous, flattened and mostly dichotomous axes that are erect or sprawled on rocky substrata, the fronds broader and more densely branched proximally ( Fig. 1 f View Fig ) and attached by narrow haptera both basally and along the lengths and at the ends of prostrate branches ( Fig. 1 f View Fig arrows, g). Axes are laxly filamentous centrally, the medulla surrounded by broad layers of enlarged subisodiametric cells bounded by surface layers that are deeper on one side than the other ( Fig. 2 e View Fig ). Tetrasporangia are formed in well-demarcated subapical nemathecia ( Fig. 3 i View Fig ) in which these are flush with the surface and tightly jacketed by two-celled cortical paraphyses ( Fig. 3 j View Fig ). Spermatangial ampullae are borne on subcortical mother cells and produce two-celled chains of rounded spermatia ( Fig. 3 k View Fig ). Mature cystocarps are protuberant, the thick pericarps ostiolate and present both marginally and on flat surfaces ( Fig. 6 a View Fig ). Frequent in the cortex are two-celled ‘glandular’ hairs that leave deeply staining basal portions when the part extended beyond the frond surface is shed ( Fig. 6 b View Fig ). Carpogonial branches are three-celled and borne on subcortical supporting cells ( Fig. 6 b View Fig ). There is uncertainty as to whether the auxiliary cell and diploidised carpogonia branch are procarpic but the gonimoblast filaments ( Fig. 6 e View Fig ) issuing from the fusion cell initially grow mostly inwardly and laterally but later form a mostly outwardly oriented placenta of mixed vegetative and gonimoblast filaments ( Fig. 6 f View Fig ). The mature cystocarp has a broad hemispherical placenta ( Fig. 6 g View Fig ) on which a surface palisade of catenate carposporangia is borne ( Fig. 6 h View Fig ), the sporangia shed through a broad ostiole ( Fig. 6 g View Fig ).