Nitella congesta (R.Br.) A.Braun, Hookers J. Bot.

Casanova, Michelle T. & Karol, Kenneth G., 2023, Charophytes of Australia’s Northern Territory - II. Tribe Nitelleae, Australian Systematic Botany 36 (4), pp. 322-353 : 331-333

Nitella congesta (R.Br.) A.Braun, Hookers J. Bot. Kew Gard. Misc. 1: 198 (1849)

Chara congesta R.Br. , Prodr. 1: 346 (1810).

Type: Bay I [Lucky Bay], South Coast, Novae Hollandiae oram septentrionalem et australem, Western Australia, Jan. 1802, R. Brown s.n. [Iter Austral. 276] (lecto: BM000904640 !; isolecto: BM000610394 !, BM 000610395 fide M. T.Casanova in D. J.Mabberley & D. T.Moore, Robert Brown Handb. 108 (2022)) .

Dioecious. Plants up to 40 cm tall, robust with very strong stems, with dense, often spherical whorls of branchlets (string-of-beads morphology), with mucus, especially in the upper parts ( Fig. 5 a ). Axes up to 1 mm in diameter, usually wiry and strong; internodes up to 10 cm long. Fertile branchlets at the apices; heteroclemous (at least 3 whorls at each node, but frequently so compacted that it is impossible to distinguish separate whorls); 3 or 4× furcate ( Fig. 5 e ). Approximately 8 branchlets in the primary whorl (i.e. the longer branchlets), with primary segments up to 10 mm long, at least half the branchlet length; secondary segments 5–8, 1 of them central, up to 1/3 of them dactyls, tertiary segments 3–7, sometimes dactyls, one of them central (in female plants) and again furcate, quaternary segments 1–5, sometimes one of them central and again furcate into 3 quinary segments = dactyls. There can be 20–40 accessory whorl branchlets, up to 3× furcate, but fewer in the upper fertile whorls; sterile branchlets are similar to fertile branchlets but the primary whorl branchlets can be longer and emergent from the congested sphere of branchlets. In older whorls, sometimes only the primary branchlet segments remain. Dactyls are 2 cells long, the end-cell long-conical and acute ( Fig. 5 f ). Heads are not formed, but the upper fertile whorls are well separated and often sequentially smaller in size and number of accessory branchlets ( Fig. 5 a ). Gametangia on separate plants at all fertile branchlet nodes ( Fig. 5 h, i ), including sometimes oosporangia at the base of the whorl on the axial nodes. Oosporangia are solitary or aggregate (up to 4 at a node) 400–500 µm long and 350–450 µm wide, with 8–10 helical stripes; coronula small with equal-sized cells ( Fig. 5 h ). Oospores pale to dark brown, appearing ‘felted’ (i.e. intermingled fibres) under light microscopy, 350–450 µm long, 300–400 µm wide with 8 or 9 ridged striae and a crest of the joined ridges at the apex of the oospore ( Fig. 5 b ). The oospore wall is superficially smooth, but densely fibrous and felted underneath ( Fig. 5 c, d ), the basal-cell impression is of 2 cells of equal size. Antheridia are solitary, up to 400 µm long ( Fig. 5 i ). Chromosome numbers n = ~9 (Tasmanian specimen, H. & A.Wapstra HAW 071 ( HO, MEL)).

Taxonomic notes

There is some variation among populations particularly in oospore size and development of flanges, along with variation in the number of branchlets. Sometimes only female plants can be found, suggesting the capacity for parthenogenesis, as in Chara canescens Loisel. ( Casanova and Nicol 2009). Specimens appear to be perennial and old specimens can be blackish with degraded whorls of branchlets (mere bristles) at the nodes.

Recognition

Nitella congesta is usually easy to identify on the basis of its densely packed whorls of branchlets and pale brown, feltedlooking oospores.

Distribution

Specimens have been recorded from Western Australia, South Australia, Victoria and Tasmania, as well as the Northern Territory.

Etymology

Presumed to be named for the tightly packed branchlets in congested whorls.

Specimens examined

WESTERN AUSTRALIA: Bremer Gorge , 1 Sep. 1965, M. Wittwer 476 ( PERTH); Lake Richmond , 11 Feb. 1978, K. F. Kenneally 6530 ( PERTH); Fitzgerald River , 11 Jan. 1980, B. G. Muir s.n. ( PERTH); Lake Joondalup, 19 Jan. 1989, Schmidt s.n. ( PERTH); Bannister River , 29 Sep. 2002, M. T. Casanova 0209291 ( MEL, NY); Palm Spring near Millstream , 17 Sep. 2003, M. N. Lyons PBS3021 ( PERTH); Lake Leschenaultia , 5 Oct. 2010, M. T. Casanova r810, r811 ( MEL, NY, PERTH) .

NORTHERN TERRITORY: Willoughby Bore, 15 Feb. 1971, G. C.Taylor 7 (DNA, MEL); Gorge behind old Serpentine Chalet, ~ 110 km W of Alice Springs , 7 Sep. 1985, G.Leach 716 (DNA) . SOUTH AUSTRALIA: Dead Man’s Lagoon near Naracoorte , 16 July 1991, M. T. Casanova 910716-1 A ( MEL); Gahnia Lagoon, 24 Feb. 1997, M. A. Brock s.n. ( NE); Henry Creek , 13 May 2004, M. Hammer s.n. ( MEL); Lake Edward , 13 June 2004, M. T. Casanova p611 ( MEL); Lake Leake , 13 June 2004, T. M. Dugdale & K . Dixon p614 ( MEL); Mt Monster quarry, 27 Oct. 2007, M. T. Casanova r022 ( MEL); Freshwater Lake, Little Dip Conservation Park , near Robe , 31 Oct. 2010, M. T. Casanova r849 ( MEL, NY) . VICTORIA: Lake Mombeong , 14 June 2004, R. L. A. Casanova t017 ( MEL) . TASMANIA: Sandford Lagoon , 1905, G. S. Perrin s.n. ( HO); Blackmans Lagoon, 16 Apr.1997, M. Cameron 5447 ( HO); Meredith R , Swansea , 10 July 2008, H. & A. Wapstra 016 ( HO, MEL, NY); Latrobe near Dooleys Hill, 17 Nov. 2008, H. & A. Wapstra 071 ( HO, MEL) .

Figures

Fig. 5. Nitella congesta. (a–d) From the isolectotype specimen R.Brown 276 (BM). (e–h) From specimen M.T.Casanova r022 (MEL), (i) from specimen H. & A.Wapstra HAW059 (HO). (a) Habit of whole plant, scale: 5 cm. (b) Scanning electron microscope (SEM) image of oospore with 8 or 9 striae, scale: 200 µm. (c) SEM image of detail of oospore wall, scale: 20 µm. (d) SEM image of detail of the construction of the oospore wall, scale: 5 µm. (e) Sterile branchlet whorl, scale: 5 mm. (f) Sterile dactyls, scale: 0.5 mm. (g) Oogonium, scale: 100 µm. (h) Fertile oogonial branchlet, scale: 1 mm. (i) Fertile antheridial branchlet, scale: 1 mm.