The Dicranemataceae (Gigartinales, Rhodophyta) revisited: molecular data indicate polyphyly in yet another wholly or primarily Australian endemic family

Anatomical methods

The taxonomic histories, various synonymies and previously published literature are covered in Kraft (1977b) and Kraft and Womersley (1994).

Site, habitat, date and collector(s) data for each of the specimens illustrated in Fig. 1–7 and 9–11 are provided in the ‘Specimen data: sources of morphological illustrations’ section in the Supplementary material. Equipment and procedures employed for anatomical observations are as detailed in Kraft and Saunders (2021). All voucher materials on which illustrations previously published in Kraft (1977b) and Kraft et al. (2014) that are reproduced below are either permanently housed in The State Herbarium of South Australia (AD) or in the case of the Hawaiian-endemic Tylotus laqueatus, the Herbarium Pacificum, Bernice Bishop Museum, Honolulu (BISH). Herbarium accession numbers provided in Kraft (1977b) and Kraft and Womersley (1994) as ADU (for the Womersley herbarium at the University of Adelaide) and MELU (for the Herbarium of The University of Melbourne) are provided unchanged from the earlier publications to avoid confusion but all are currently placed in AD. Many of the collections cited in the ‘Specimen data: sources of morphological illustrations’ section in the Supplementary material are also accompanied by numbers from Kraft’s field notebooks (as K-GEN-xxx or K-LHI-xxx). These specimens have also been transferred to AD where AD designations and labels will ultimately be received.

Specimens cited in the previous monographs of Mychodea and the Mychodeaceae (Kraft and Saunders 2017), and the Acrotylaceae (Kraft and Saunders 2021) have been transferred to AD from the Kraft private herbarium.

Molecular methods

Collections used in our molecular analyses are listed in Table S1 in the Supplementary material. These were variously dried as vouchers (pressed or in vials) with subsamples placed in silica gel for subsequent DNA extraction as outlined in Saunders and McDevit (2012). All specimens were initially screened with COI-5P or rbcL to facilitate an initial assignment to genetic species groups (Saunders and Moore 2013). Data were generated for COI-5P, rbcL and LSU as outlined in Saunders and Moore (2013) or sourced from GenBank in a few cases (indicated in Fig. 8) for each dicranematacean species uncovered and related gigartinalean taxa to round out the phylogenetic analyses. An exception occurred for amplification of the LSU in GWS016630 and GWS025656 for which the new forward primer PeltF1 (TTCGGGSTGTCAGTGYGGGWA) replaced the external forward primer T01N to acquire some data for these interesting specimens. In both cases PeltF1 was used in PCR reactions with T20 or T10N or T08 to acquire PCR products for sequencing (Saunders and Moore 2013). Individual gene alignments were COI-5P (78 taxa, 664 bp), rbcL (90 taxa, 1358 bp) and LSU (70 taxa, 1955 bp). Each alignment was subjected to maximum likelihood (ML) analyses with RAxML (ver. 8.2.11, see https://github.com/stamatak/standard-RAxML; Stamatakis 2014; GTR + I + G model with partitioning by codon for protein coding genes) with branch support calculated using 500 bootstrap replicates. No strong conflicts were detected, and a concatenated COI-5P + rbcL + LSU alignment was constructed (91 sequences, 3977 bp) and analysed as above but with partitioning by gene and codon for protein coding genes and with 1000 bootstrap replicates. This tree was rooted on the Gigartinaceae–Phyllophoraceae clade (Kraft and Saunders 2021) and these families, and taxa of the Chondrymeniaceae and Furcellariaceae (Table S1), were cropped from the final figure to facilitate presentation (Fig. 8).

Dicranema revolutum (C. Agardh) J. Agardh (1852, p. 634)

The generitype species is an obligate epiphyte of the seagrass Amphibolis antarctica (Labill.) Sond. & Asch. from subtropical Western Australia, eastward across temperate southern coasts to Victoria and south to Flinders I. in The Bass Strait (Kraft and Womersley 1994). The thalli are erect, filiform and laxly to compactly dichotomous but not complanate (Fig. 1a). Axes are composed of a narrow central core of compact filaments surrounded by a broad band of large hyaline, (sub-)isodiametric cells bounded by a thin compact cortex of small, pigmented cells (Fig. 2a). Tetrasporangia occur subterminally in slightly swollen nemathecia at branch forks (Fig. 3a) and are basally pit-connected to mother cells at the base of vertical cortical filaments (Fig. 3b). At maturity the sporangia are immersed two or three cortical layers below surface cortical cells (Fig. 3b). Spermatangia are catenate and form in scattered ampullar clusters deeply inset from the branch surface (Fig. 3c). Gametophytes are monoecious, the cystocarps protuberant, ostiolate and single or in short series near branch apices (Fig. 4a, b). Large cavities remain when outer pericarps and mature carposporophytes and carposporangia are shed (Fig. 4b). Carpogonial branches are two-celled, the trichogynes smoothly cylindrical and arching toward the branch surface from deeply positioned supporting cells (Fig. 4c). Presumably diploidised carpogonia appear to initially fuse at the bases of the trichogynes to apparently non-differentiated auxiliary cells situated within adjacent cortical filaments (Fig. 4d), the auxiliary cells subsequently commencing to join with cells in neighbouring filaments to form elaborate fusion cells (Fig. 4e, f) that issue numerous gonimoblast filaments in all directions (Fig. 4g). A matrix of intermixed and secondarily pit-connected and fused cells of gonimoblast and vegetative filaments forms from the fusion cell and develops mostly toward the centre of the host axis (Fig. 4h) whereas a cavity above the placenta opens up above the growing carposporophyte (Fig. 4i). The leading surface consolidates with further growth of the mixed placental filaments and gives rise to a layer of free dendroid gonimoblasts (Fig. 4j). Large obovoid to lachrymose terminal carposporangia subsequently cover the surface (Fig. 4k) beneath the roof of the pericarp, where release is made through an ostiole on the side of the cystocarp opposite the diploidised auxiliary cell (Kraft 1977b, fig. 3c) or through the breakdown of the pericarp that begins at the ostiole (Fig. 4l).

Dicranema cincinnalis Kraft (1977b, p. 228)

Thalli are confined to the stems of the seagrass Amphibolis antarctica and recorded from western Yorke Peninsula, South Australia to Westernport, Victoria. The erect axes form tightly curled, ball-like clusters of slender (200–250 μm in diameter) dichotomous filaments (Fig. 1b, c, 3d). Vegetative structure is basically that of D. revolutum but layers encircling the medullary filaments are fewer and somewhat laxer in these much thinner axes (Fig. 2b). Tetrasporangia form in slightly swollen and hooked ends of branch forks (Fig. 3d), the cells basally pit-connected and at maturity borne on inner-cortical mother cells similarly inset from the surface as in D. revolutum (Fig. 3e). Deeply inset clusters of catenate spermatangia (Fig. 3f) are also similar to but smaller than those of the generitype species. Carpogonial branches, fusion-cell formation and gonimoblast initiation are much as in D. revolutum (Kraft 1977b, fig. 4F, G) but placental size and depth (Fig. 4m; Kraft 1977b, fig. 5B) are much reduced owing to the thinness of the axes. Mature cystocarps take virtually the whole interior of the bearing axis and no ostiole has been observed although filaments to one side of the surrounding pericarp (Fig. 4n, arrow) are much laxer and may be where the pericarp splits to release carpospores. On rare occasions, two carposporophytes originating from opposite sides of the bearing branch meet in the middle and completely fill the centre of the axis (Kraft 1977b, fig. 13E).

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. 1d, 5a). Anchorage is by a series of short basal stolons and haptera (Fig. 1e). Axes are bluntly rounded and slightly flared at the multiaxial tips, and mature cross- and long-sections (Fig. 2c) consist of a narrow core of deeply pigmented filaments surrounded by a wide expanse of colorless, subisodiametric cells (Fig. 2c) bordered on both sides by a cortex of ovoid surface cells subtended by a single layer of small isodiametric cells (Fig. 2d). Tetrasporangia are basally pit-connected to cells of the subsurface layer and mostly accompanied by a single elongate companion cell (Fig. 3g). Male gametes form in subsurface ampullae and consist of elongate spermatangia that are released through surface pores in the colorless cuticle (Fig. 3h). The monoecious gametophytes (Fig. 5a) initiate cystocarps in subapical swellings (Fig. 5b) and produce carposporophytes within globular, ostiolate pericarps at maturity (Fig. 5c). Carpogonial branches are three-celled (Fig. 5d; Kraft 1977b, fig. 6G) and form deep in the cortex on supporting cells that subtend slightly swollen auxiliary cells (Fig. 5d) with which the presumably fertilised carpogonia directly fuse (Fig. 5d, 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. 5d) 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. 5e, f). As the carposporophytes placentate (Fig. 5g, h), an ostiole progressively differentiates from the surface and extends deeply downwardly to the gonimoblasts (Fig. 5g). The ultimate development of gonimoblasts on the central placental core consists of dense arrays of long, parallel files of elongate cells (Fig. 5i) that bud off spherical carposporangia and contain varying numbers of knotted cells (Fig. 5j) that appear to be islands of arrested growth.

Reptataxis rhizophora (A.H.S.Lucas) Kraft (1977b, 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. 1f) and attached by narrow haptera both basally and along the lengths and at the ends of prostrate branches (Fig. 1f 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. 2e). Tetrasporangia are formed in well-demarcated subapical nemathecia (Fig. 3i) in which these are flush with the surface and tightly jacketed by two-celled cortical paraphyses (Fig. 3j). Spermatangial ampullae are borne on subcortical mother cells and produce two-celled chains of rounded spermatia (Fig. 3k). Mature cystocarps are protuberant, the thick pericarps ostiolate and present both marginally and on flat surfaces (Fig. 6a). 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. 6b). Carpogonial branches are three-celled and borne on subcortical supporting cells (Fig. 6b). There is uncertainty as to whether the auxiliary cell and diploidised carpogonia branch are procarpic but the gonimoblast filaments (Fig. 6e) 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. 6f). The mature cystocarp has a broad hemispherical placenta (Fig. 6g) on which a surface palisade of catenate carposporangia is borne (Fig. 6h), the sporangia shed through a broad ostiole (Fig. 6g).

Pinnatiphycus menouana N’Yeurt, Payri & P.W.Gabrielson (2006, p. 423)

This monotypic genus is recorded from New Caledonia and Fiji. Thalli are shown to be complanate, compressed to flattened and sprawling, arising from a basal disk or short stolon (N’Yeurt et al. 2006, fig. 4, 5) that anchors a short terete stalk that broadens through an apophysis (N’Yeurt et al. 2006, fig. 4, 5) to blades above that are attached to the substratum at intervals by slender haptera (N’Yeurt et al. 2006, fig. 5). Unique among the genera is the abundance of regularly spaced distichous, terete and simple or occasionally bifid horizontal marginal laterals (Fig. 1h; N’Yeurt et al. 2006, fig. 3–6). Axes consist of a broad core of compact filaments of elongate cells tightly encircled by a broad zone of radially aligned (in cross section) filaments of equal width and a three- or four-celled outer cortex (N’Yeurt et al. 2006, fig. 7–9). Spermatangia occur in crowded, deep ampullar pits (N’Yeurt et al. 2006, fig. 16) and tetrasporangia are flush with the surface and accompanied by elongate paraphyses (N’Yeurt et al. 2006, fig. 17, 18) within swollen tips of laterals (N’Yeurt et al. 2006, fig. 6, 19). Carpogonial branches are three-celled (N’Yeurt et al. 2006, fig. 11, 12) but auxiliary-cell position and features of diploidisation are not documented. A fusion cell persists in the centre of an extensive placenta (N’Yeurt et al. 2006, fig. 13), the terminal carposporangia borne on short spreading filaments three or four cells in length (N’Yeurt et al. 2006, fig. 14) and discharged through an apical ostiole (N’Yeurt et al. 2006, fig. 13).

Tylotus obtusatus (Sond.) J.Agardh (1876, p. 428)

Thalli of this variably contoured species are recorded from Champion Bay (Geraldton), Western Australia, to Inverloch, Victoria (Kraft and Womersley 1994, p. 330). The thalli are typically darkly pigmented, almost black and coarsely foliose, smooth margined, basically dichotomous and erect or repent from prostrate basal portions (Fig. 1i) anchored by scattered stout haptera (Fig. 7a). Some thalli are shades of mahogany brown, especially when tetrasporangial (Fig. 1j). Thalli are ‘cellular’ (pseudoparenchymatous) throughout, derived from a broad cluster of marginal initials (Fig. 2f), the interior cells of mature axes becoming compact and thick-walled (Fig. 2g). Tetrasporangia form in elongate nemathecia (Fig. 1j) and grow on and among lengthy palisade filaments, the sporangia mostly flush with the surface but with scattered others, possibly non-functional, occurring at the bases or subsurface along the lengths of the filaments (Fig. 3l). Male ampullae are borne on subsurface mother cells and form tight clusters of two-celled spermatangial filaments (Fig. 3m). Cystocarps form on dorsal surfaces of fronds (Fig. 7a) and produce three-celled carpogonial branches at various depths in the cortex, the carpogonia lying in proximity to the supporting cell (Fig. 7b), and borne on basal and hypogynous cells that partially wrap around what will become the auxiliary cell (Fig. 7c, d). There is direct evidence of procarpy in that the presumably diploidised carpogonium clearly fuses with the supporting cell (Fig. 7d, arrow) and that this fusion precedes the formation of a compact fusion cell. Subsequent gonimoblast growth is lateral from the fusion cell (Fig. 7f) and spreads across a basal, presumably nutritive, layer of gametophytic cells as the ostiole differentiates and a cavity opens beneath the thick pericarp (Fig. 7g, h). The fusion cell persists throughout extensive carposporophyte growth in which gonimoblast and host gametophyte interconnections appear to occur mostly or only along the carposporophyte base (Fig. 7i, j) rather than in a placental mixture. The leading surface of the carposporophyte begins to invaginate with maturity (Fig. 7j, k), producing increased surfaces on which gullies and pockets (Fig. 7l) are lined with short filaments with terminal spherical carposporangia (Fig. 7m).

Tylotus laqueatus Kraft, K.Y.Conkl. & A.R.Sherwood (2014, p. 21)

This species is endemic to the Hawaiian Islands, based on very infrequent records made from Oahu and Maui. Fronds are regularly dichotomous to subdichotomous, of uniformly narrow widths and often hummocked and imbricating (Fig. 1k), becoming broader and more irregularly contoured proximally (Kraft et al. 2014, fig. 7, 9). Anchorage is by numerous scattered haptera at the bases (Fig. 1l) and along the lengths (Fig. 3n, Kraft et al. 2014, fig. 11–17) of distal fronds. Cross sections are composed of compact pseudoparenchyma throughout the interior, bounded by a shallow, even cortex on both sides (Fig. 2h). Occurring in the outer cortex are numbers of short, ‘glandular’ hairs (Kraft et al. 2014, fig. 19–21). Tetrasporangia occur in irregularly rounded sori scattered along the dorsal lengths of fronds (Fig. 3n), the tetrasporangia flush with the surface on relatively short parallel nemathecial filaments (Fig. 3o), with relatively few buried at deeper levels (Kraft et al. 2014, fig. 24). Spermatangia occur in shallow subcortical ampullae (Kraft et al. 2014, fig. 25–27). Carpogonial branches are three-celled and infrequently encountered, although the carpogonium appears to be in proximity to the supporting cell (Kraft et al. 2014, fig. 28). Early gonimoblast development and basal placentation (Kraft et al. 2014, fig. 30), and deep invaginations of the leading carposporophyte edge (Kraft et al. 2014, fig. 29) and short carposporangial filaments (Kraft et al. 2014, fig. 34) appear to be very similar to those of T. obtusatus but a major difference is the implantation of some gonimoblasts of the former into the inner surface of the domed pericarp, where these reverse direction and also produce spore-bearing filaments into the cystocarp chamber (Kraft et al. 2014, fig. 29, 31, 32).

Tylotus lichenoides Okamura (1921, p. 98, pl. 173, fig. 8–15)

This long-obscure species is recorded from Japan, China and Taiwan (M. D. Guiry and G. M. Guiry, AlgaeBase, see https://www.algaebase.org). The thallus illustrated (Fig. 1m) appears very similar to common forms of T. obtusatus in the dark coloring and generally dichotomous flabellate axes but a wide variety of frond morphological characteristics and branching patterns has been illustrated by other authors (Arasaki 1964, p. 97, number 349; Segawa 1967, pl. 66, number 425; Tanaka and Nakamura 2004, p. 169; Tseng 1983, pl. 61, fig. 1). The best illustrations of internal structures are those in the protologue of Okamura (1921, pl. 173).

Fig. 9–11 illustrate the salient features of three previously undescribed genera and species that were discovered during the course of collections (see ‘Specimen data: sources of morphological illustrations’ section and Table S1 in the Supplementary material) for molecularly assisted taxonomic studies. Formal descriptions of these new taxa are provided below.

Dicranemataceae Kylin, Acta Univ. Lund. 2 28(8), p. 65 (1932), emend Kraft & G.W.Saunders

The Dicranemataceae consists of Dicranema and the two Australian-endemic species D. revolutum and D. cincinnalis. This single genus member differs from the family as characterised by Kraft (1977b) and Kraft and Womersley (1994) in that the genus Dicranema is the sole member. Critical anatomical and morphological features of the emended taxon are provided in the morphological results as above (Fig. 1a–c, 2a, b, 3a–f and 4a–n). Molecular results situate the Dicranemataceae sensu stricto in an isolated position among the Acrotylaceae, Mychodeaceae and the Mychodeophyllaceae, with which this shares very few anatomical particulars. Dicranema is far removed from the positions occupied by all members of the other two families that the group is being divided into.

Peltastaceae Kraft & G.W.Saunders, fam. nov.

Type: Peltasta J.Agardh.

Thalli either multiaxial or uniaxial, terete to compressed, the medulla of narrow, darkly pigmented filaments or consisting of a single stout central-axial filament, each cell of which produces a single periaxial cell (rarely two) and cortical filament. Anchorage by basal haptera or stolons. Tetrasporangia zonate, basally pit-connected, scattered or in nemathecia. Thalli monecious, the spermatangia in ampullae sunken in the cortex or in cavities borne in extensive outgrowths from the cortex surface. Carpogonial branches three-celled, the auxiliary cell procarpic in the generitype (Peltasta australis), the gonimoblast initials and filaments radiating in all directions from a complex of the auxiliary cell and fused adjacent vegetative cells, deeply embedded beneath a down-growing ostiole and ultimately basally and interiorly placentate. Carposporangia borne singly on parallel filaments across the surface of the placenta.

Peltastanomala G.W.Saunders & Kraft, gen. nov.

Type: Peltastanomala virantra G.W.Saunders & Kraft.

A monotypic genus, the description as for the single species, P. virantra.

Peltastanomala virantra G.W.Saunders & Kraft, sp. nov.

Type: NEW SOUTH WALES: Coffs Harbour (30°18′17″S, 153°08′53″E), thalli on rock at 4 m off Muttonbird Island, 12 Dec. 2012, G.W. Saunders & K.R. Dixon s.n., (holo: Connell Memorium Herbarium, University of New Brunswick. UNB-GWS032778 (fig. 9A) (cystocarpic); iso: UNB-GWS032779 (tetrasporangial). Type DNA barcode: PP866174 (COI-5P), PP866280 (rbcL).

Thalli cartilaginous, growing in dense bushy tufts composed of erect, terete to slightly compressed axes 2–6 cm in height (Fig. 9a) and arising from a basal tangle of stout haptera and solons (Fig. 9b). Thalli uniaxial, the axes 400–1000 µm in diameter, consisting of a prominent central-axial filament surrounded by a broad, dense layer of pseudoparenchymatous cells packed with floridean starch grains, this bounded by a one or two-layered inner cortex and a single-layered surface (Fig. 9c). Central-axial cells 45–55 µm in diameter, each with a single periaxial filament in a rotating sequence (Fig. 9c–e). Tetrasporangia 18–26 by 5.5–7.7 µm, produced in encircling subapical nemathecia (Fig. 9f), the tetrasporangia zonate, basally pit-connected to bearing cells and each accompanied by a one or two-celled paraphysis. Tetrasporangia normally smoothly rectilinear (Fig. 9f, g), occasionally more rotund, irregularly contoured and possibly non-functional in older axes (Fig. 9h). Gametophytes monoecious (Fig. 10a), the spermatangia borne singly at the ends of narrow dendroid filaments within thinly bounded cavities 65–80 µm deep that arise from surface cortical cells (Fig. 10a, b). Procarpy and diploidisation not observed, early gonimoblasts growing radially from a complex of fused auxiliary-cell and adjacent vegetative cells (Fig. 10c), with maturity the carposporophyte basally placentate within a thick pericarp (Fig. 10a, d), at maturity forming a palisade layer 100–150 µm deep of filaments bearing single carposporangia beneath an initially narrow ostiole (Fig. 10e).

Chambersius G.W.Saunders & Kraft, gen. nov.

Type: Chambersius thyrsus G.W.Saunders & Kraft.

A monotypic genus, the description as for the single species Chambersius thyrsus.

Chambersius thyrsus G.W.Saunders & Kraft, sp. nov.

Type: VICTORIA: Point Lonsdale (38°16′35″S, 144°37′14″E), thalli on sandstone cobbles at 4.27 m on the reef seaward of the end of Lawrence Road, 02 Feb. 2010, G.W. Saunders, L.G.K. Kraft & K.R. Dixon s.n. (holo: UNB-GWS016630 (fig. 11A), non-reproductive. Type DNA barcode: HM918282 (COI-5P), PP866286 (rbcL).

Thalli filiform (Fig. 11a, b), 3–8 mm in length, the erect axes growing from a single, obliquely dividing apical cell (Fig. 11c) and arising from a creeping base anchored by tight clusters of parallel filaments forming short haptera (Fig. 11d). Erect axes 120–170 µm in diameter, the prominent central-axial cells surrounded by a 2–3 layered cortex of sub-isodiametric cells and a single-celled surface-cortical layer (Fig. 11e). Central-axial cells elongate, with trumpeted ends and producing a single periaxial cell (rarely two), and subsequent filament giving rise to the cortical layers (Fig. 11f, g). Cortical hairs extending from ovoid to triangular bases in the surface cortex and passing through the cuticle through a papillate surface pore (Fig. 11h). Reproductive structures are not known.

Huismanophycus G.W.Saunders & Kraft, gen. nov.

Type: Huismanophycus marinus G.W.Saunders & Kraft

A monotypic genus, the description as for the single species Huismanophycus marinus.

Huismanophycus marinus G.W.Saunders & Kraft, sp. nov.

Type: WESTERN AUSTRALIA: ‘The Basin’, Rottnest Island (31°59′21″S, 115°32′09″E), thalli on Sonderophycus capensis at −3.0 m, 18 Nov. 2010, K. & R. Dixon & G. Bolton (holo: UNB-GWS025656 (fig. 11I), non-reproductive. Type DNA barcode: PP866183 (COI-5P), PP866282 (rbcL).

The single collection on which this taxon is based consists of recumbent to prostrate epiphytes on the fan-shaped dorsal surfaces of Sonderophycus capensis (Mont.) M.J.Wynne (Fig. 11i). Thalli fragmenting easily, one of the largest portions reaching 1.55 cm in length with axes 30–70 µm in width (Fig. 11j). Irregularly produced laterals tapering to needle-like points imparting a Hypnea-like appearance to the fronds (Fig. 11j). Growth from a single obliquely dividing apical cell (Fig. 11k), the initially terete axes becoming compressed and 90–110 µm wide by 60–70 µm thick (Fig. 11j, l). The central-axial filament persisting in lower cross-sections and surrounded by one or two layers of rounded hyaline cortical cells and a surface layer of similarly sized rounded to angular cells (Fig. 11l, m). Axial cells occasionally pit-connected to two periaxial cells (Fig. 11l, arrows) but usually only one is present and rotated on successive axial cells (Fig. 11m, arrows). Surface cells occasionally extending into deciduous hairs (Fig. 11n). Prostrate axes anchored basally and along the lengths by compact short haptera that issue from the under sides (Fig. 11o). Reproductive structures not known.

Tylotaceae Kraft & G.W.Saunders, fam. nov.

Type: Tylotus J.Agardh

Family consisting of the genera Tylotus, Pinnatiphycus and Reptataxis.

Thalli multiaxial, attached basally or also along the fronds by stout terete haptera. Fronds flattened to compressed, centrally either completely pseudoparenchymatous (Tylotus) or with a narrow filamentous medulla surrounded by a pseudoparenchymatous cortex. Tetrasporangia zonate, in nemathecia. Gametophytes monoecious, spermatangia in ampullar pits containing a single mother cell ringed distally by one- or two-celled spermatangia. Carpogonial branches three-celled, auxiliary cells clearly procarpic in Tylotus, not yet determined in the other genera. Gonimoblasts multiple and radial in Reptataxis and Pinnatiphycus, becoming basally placentate; gonimoblasts in Tylotus initially horizontal from a large fusion cell, extending across and fusing with cells of a basal layer of gametophyte cells. Cystocarps ostiolate, carposporophytes domed and with much-invaginated surfaces, the carposporangia terminal on elongate subtending cells; carposporophytes of Pinnatiphycus and Reptataxis centrally composed of mixed or fused gonimoblast and vegetative cells or filaments, the carposporangia forming fanned chains of 2–3 in Pinnatiphycus and catenate parallel chains of 4–6 in Reptataxis.