Nitella biformis A.Braun

Casanova, Michelle T. & Karol, Kenneth G., 2023, Charophytes of Australia’s Northern Territory - II. Tribe Nitelleae, Australian Systematic Botany 36 (4), pp. 322-353 : 328-329

Nitella biformis A.Braun , Hookers J. Bot. Kew Gard. Misc. 1: 197 (1849)

Nitella conglobata var. biformis (A.Braun) A.Braun in C. F. O.Nordstedt, Abh. Königl. Akad. Wiss. Berlin 1882: 77 (1883); Nitella subtilissima f. biformis (A.Braun) R.D. Wood, Taxon 11: 21 (1962).

Type: WESTERN AUSTRALIA: Swan River, J. Drummond 8 (lecto: BM! [oosporangial specimen]); isolecto: BM! [antheridial specimen], fide R.D.Wood & K.Imahori, Revis. Charac. 1: 652 (1965)) .

Nitella congesta f. subtilissimoides R.D. Wood, Taxon 11: 22 (1962) ; Nitella lhotzkyi f. subtilissimoides ( R.D.Wood) R.D.Wood , Revis. Charac. 1: 668 (1965); Nitella subtilissimoides R.D.Wood , Revis. Charac. 1: 779 (1965), nom. inval.

Type: WESTERN AUSTRALIA: in shallow water near margin of Lake Parkeyerring, near Wagin , 28 Dec. 1955, N. Burbidge 4951 (holo: AD 20411 !; iso: NY!) .

[ Nitella lhotzkyi auct. non A.Braun: R.D. Wood, Nova Hedwigia 22: 76 (1971)]

Dioecious. Plants up to 10 cm high, male plants with more open and diffuse sterile whorls than those in female plants; upper whorls with mucus ( Fig. 3 a ). Axes 300–330 µm wide. Internodes up to 2 cm long, 1–3× the length of the branchlets. Fertile branchlets heteroclemous, 7 or 8 primary branchlets in a whorl; the primary whorl branchlets 1 or 2× furcate; 1 or 2 simple (not furcate) branchlets in the secondary whorl on male plants (i.e. scarcely heteroclemous, Fig. 3 c ); the secondary branchlets 1× furcate on the female plant; sterile branchlets heteroclemous with 7 or 8, 1 or 2× furcate primary branchlets in a whorl with 2–5 simple or 1×furcate secondary branchlets ( Fig. 3 b ); primary segments up to 0.8 mm long, secondary segments 4–5, up to 0.5 mm long, at least 2 of them again furcate into 3–5 tertiary segments (=dactyls) up to 400 µm long. Fertile dactyls up to 400 µm long, bicellulate; the end-cell conical and acute ( Fig. 3 c ). Sterile dactyls up to 0.8 mm long, bicellulate; the end-cell conical and acute ( Fig. 3 d ). Heads not formed, the whorls all similar. Gametangia on separate plants, at axial nodes (oosporangia) and first and second branchlet nodes (oosporangia and antheridia). Oosporangia up to 350 µm long × 350 µm wide with 8 helical stripes, coronula cells similar in both rows ( Fig. 3 e ). Oospores up to 320 µm long and 300 µm wide with 6 or 7 flanged striae (flanges can break off) and a distinctive ‘crest’ or ‘beak’ at the apex ( Fig. 3 g ), the oospore wall construction is fibrous ( Fig. 3 h ), with apparently a single basal-cell impression present ( Fig. 3 i ). Antheridia up to 250 µm in diameter ( Fig. 3 c ). Chromosome numbers n = 9 (specimen M. T.Casanova p795, Fig. 3 f ).

Nomenclatural notes

Braun (1849) initially named this species, and in a later work amalgamated it with Nitella lhotzkyi and renamed the amalgamated taxon N. conglobata A.Braun , nom. illeg. Wood (1962) synonymised N. biformis with N. subtilissima (as N. subtilissima f. biformis (A.Braun) R.D.Wood) on the basis that it was unlikely that Drummond could have collected four new species sequentially in a single site (Swan River) ( Wood 1971, p. 71). Wood (1962) described another specimen of this species as N. congesta f. subtilissimoides R.D.Wood, later transferring it to N. lhotzkyi f. subtilissimoides ( R.D.Wood) R.D.Wood ( Wood 1971). The morphology of these plants and their oospores are very similar, so they are here amalgamated into one species, for which the name N. biformis has priority.

Recognition

A species with short branchlets and fine axes, with large antheridia and very few secondary branchlets, forming dense, mossy cushions in shallow water, occasionally as individual shoots among other species. It is scarcely heteroclemous and the smooth-looking oospores are distinctive for this dioecious entity in the group of heteroclemous Nitella species. Oospores have essentially fibrous wall construction, but are smaller than those of N. heterophylla and N. congesta .

Distribution

Known from Western Australia, semi-arid South Australia and the Northern Territory, although this inconspicuous species is probably more widespread.

Etymology

Assumed to be named for the two kinds of branchlets in the whorls (i.e. heterophyllous branchlet whorls).

Specimens examined

WESTERN AUSTRALIA: Fortescue Marsh-west, Pilbara Biological Study site PSW003, seed-bank culture, 16 Oct. 2005, M. T . Casanova p770 ( MEL, PERTH); in shallow, brackish, temporary lake growing on sandy mud, 3 miles [~ 4.8 km] SE of Morawa , 22 July 1953, R. Melville & J . Calaby 4271 ( BM); Murchison River , Oldfield s.n. ( BM) . NORTHERN TERRITORY: 7 km SW of Newhaven Homestead , common in a small seasonal lake, sandy bed, 2 Oct. 2000, P. K. Latz 16805 (DNA); 22 km S of Palmer Valley Homestead, 6 Mar. 1995 , P. K. Latz 14064 (DNA). SOUTH AUSTRALIA: Kurdimichi Outstation , seed-bank culture, 11 Nov. 2005 , M. T. Casanova p795 ( MEL).

Figures

Fig. 3. Nitella biformis. (a–c, f) From specimen M.T.Casanova p795 (MEL). (d, e, g–i) From the lectotype specimen J.Drummond 8 (BM). (a) Habit of whole plant, scale: 1 cm. (b) Sterile branchlet whorl, scale: 1 mm. (c) Fertile antheridial branchlet whorl, scale: 1 mm. (d) Dactyls, scale: 100 µm. (e) Oogonium, scale: 100 µm. (f) Light micrograph of chromosomes, 1000× magnification. (g) Scanning electron microscope (SEM) image of oospore, scale: 100 µm. (h) SEM image of detail of oospore wall, scale: 20 µm. (i) SEM image of basal-cell impression, scale: 50 µm.