Charophytes of Australia’s Northern Territory - I. Tribe Chareae Author Casanova, Michelle T. Author Karol, Kenneth G. text Australian Systematic Botany 2023 2023-03-30 36 1 38 79 http://dx.doi.org/10.1071/sb22023 journal article 10.1071/SB22023 1446-5701 10904227 Chara setosa Klein ex Willd., Mém. Acad. Roy. Sci. Hist. ( Berlin ) 1803: 85 (1805) Type : Kundelpadi Tam[ il Nadu ?], India , 7 Jan. 1799 , J .Klein 500 (holo: B-W!) . Monoecious. Plants up to 30 mm high, slightly calcified ( Fig. 19 a ). Axes corticated, cortex cells uniformly 3× the number of branchets in the adjacent nodes, isostichous 26–30 cells around ( Fig. 19 d ), spine cells 75–90 μm long, 60–75 μm wide at the base, internodes 10–80 mm long, up to 0.8 mm in diameter. Stipulodes in 2 tiers, 2 sets per branchlet, uppers longer (to 480 μm long), lower row shorter (250 μm long, 120 μm wide). Branchlets 8–10 in a whorl, corticate, up to 40 mm long, 8–10 cells long including end segment ( Fig. 19 b ), basal branchlet cell shorter than the next cell, corticated, the cortical cells apparently without chlorophyll (‘discoloured’ or ‘diaphanous’), sometimes obscured by the upper row of stipulodes ( Fig. 19 c ), branchlet cells , corticated, sometimes swollen, constricted at the nodes, particularly on young branchlets, branchlet end segments usually 2-celled, ecorticate, bract cells obscure, 6, when present anteriors longer than posteriors ( Fig. 19 e ), bracteoles 2, shorter than the mature oosporangium. Gametangia conjoined singly at second, third and sometimes fourth branchlet node. Oosporangia 670–790 µm long × 550–600 µm wide, with 12 or 13 stripes of helical cells, coronula cells connivent and blunt, ~100 µm high. Oospores not seen on Australian material, Wood and Imahori (1964) reported they are black, 630–675 µm long and 435–495 µm wide, with 9 or 10 rather prominent ridges, fossa 73 µm across; oospore wall dark brown, opaque and smooth. The illustration provided depicts a germinated oospore from the base of a plant collected in Madagascar ( Fig. 19 f–i ). That oospore is ~660 µm long and 520 µm wide with ~10 striae of prominent ridges with a ribbon-structure present on the striae ( Fig. 19 f ). The oospore wall is minutely granulate ( Fig. 19 g ) and the ribbon surface is nodulate ( Fig. 19 i ). Antheridia 200–300 µm in diameter, octoscutate. Vegetative reproduction not known. Chromosomes not known. Distribution Chara setosa is a rare species that occurs in lakes and streams in Africa, Madagascar , Asia, Papua New Guinea , and tropical Australia . There is an additonal report of an Australian specimen from the Northern Territory in Wood (1971) lodged in BM ( n.v. ). Water chemistry has not been recorded. Etymology ‘Setosa’ in Latin means silky, perhaps referring to the smooth appearance of the species. Notes Chara setosa is superficially similar to C. globularis (i.e. with straight and narrow corticated branchlets and axis) but is distinguished by the lack of colouration in the basal branchlet-cell cortex (possibly owing to a lack of chlorophyll). It is similar to C. zeylanica , except that C. zeylanica has no cortex on the basal branchlet cells. The ‘diaphanous’ or ‘discoloured’ basal branchlet cell can be obscured by the upper row of stipulodes, but can be detected by pulling down a branchlet to show the inner surface of the basal cell. Specimens examined NORTHERN TERRITORY : Roper River , 16 Jan. 1989 , B.G.Thompson 2779 ( DNA ) [four species were collected from the same locality, under the same collection number, on two sheets; one of these is C. setosa ]; WESTERN AUSTRALIA : Harding River Pool ( PSW091 T2 ), 16 May 2006 , D.A.Mickle & N.Y.Huang 33-3112 ( PERTH ). PAPUA NEW GUINEA : Bliri River , Kaiye Village , Aitape , Sepik , 18 July 1961 , P.J.Darbyshire 8171 & R.D.Hoogland ( B , CANB ). MADAGASCAR : Anse NW du lac Itasy (a env. 5 km au S d’Ampefy) Accroche a un radeau flattant (eau profunde de plus de 1 m ) [In a bay NW of Lake Itasy (~ 5 km S of Ampefy), hanging off a floating raft (in water greater than 1 m deep)], 3 Feb. 2000 , A.Raynal-Roques , J.Jeremie & M.Grouzis 24910 ( BM ).