Plants to 20 mm long, blackish green except for the green shoot tips, forming dense smooth mats or erect tufts on rock in flowing water. Stems rigid, occasionally branched; in section with a narrow central strand; axillary rhizoids sparse. Leaves erecto-patent when dry or wet, imbricate, linear, in up to 40 pairs, overlapping in mid-stem; upper leaves c. 2 mm long,
0.2–0.3 mm wide; apex acute to narrowly obtuse; apical and dorsal laminae bistratose to multistratose near the costa, unistratose to the margins; vaginant laminae uni- to bistratose adjacent to the costa, reaching to c. 1/2 leaf length, half open; dorsal lamina reaching the leaf base and shortly decurrent on the stem; margins minutely crenulate; lamina cells ±rounded, irregular, markedly thick-walled, 12–14 μm diam., smooth or slightly convex, bistratose to multistratose in the dorsal and apical laminae, except for a broad unistratose border, cells of the marginal rows smaller, 6–8 μm diam.; costa of modified bryoides-type, yellow or reddish, strong, subpercurrent.

Autoicous. Perigonia terminal. Perichaetia terminal on main stem or axillary branches; perichaetial leaves similar to stem leaves. Setae stiff, short, to 2 mm long. Capsules small, c. 0.6 mm long, rounded-oblong; exothecial cells in c. 50 columns around the circumference. Operculum conical-rostrate, 0.5–0.6 mm long, as long as the theca. Peristome of modified scariosus-type, red; teeth 70–150 μm long, 60–90 μm wide at the base, trabeculae in basal part double and forked, the filaments with oblique thickenings and strongly papillose. Calyptra smooth, mitrate.

Native.

Grows on rock, submerged or in the splash zone in fast-flowing oligotrophic waters.

Fissidens strictus Hook.f. & Wilson, Fl. Tasman. 2: 167 (1859). Type: York Town Rivulet, Tas., R.Gunn 1610 ; lecto: BM-Wilson, fide J.E.Beever, New Zealand J. Bot. 33: 291 (1995); isolecto: HO.

Vic.: Masons Falls, Kinglake Natl Park, I.G.Stone 7547 (AD, MEL).

Tas.: Hartz Mts, 17 Feb. 1985, J.E.Beever (HO); Arve Valley, I.G.Stone 25300 (MEL).

Beever (1995) provided an account of this species in New Zealand. The modified scariosus-type peristome seems anomalous in the revised subgeneric classification of Suzuki & Iwatsuki (2007), where the species is placed in subgenus Pachyfissidens section Pachyfissidens. Pursell & Bruggeman-Nannenga (2004) included the species in subgenus Aloma, based on the bryoides-type costa, the modified scariosus-type peristome, the smooth lamina cells and unbordered laminae. This, placement is followed here, although the number of columns of exothecial cells (c. 50) differs from the usual number (< 40) for subgenus Aloma. However, exceptions to these general rules do occur (Pursell & Bruggeman-Nannenga, 2004).

J.E.Beever, New Zealand J. Bot. 33: 292, fig. 1a–w (1995); J.E.Beever, B.Malcolm & N.Malcolm, The Moss Genus Fissidens in New Zealand: an illustrated key 60 (2002).

Beever, J.E. (1995). Studies of Fissidens (Bryophyta: Musci) in New Zealand: F. strictus Hook.f. & Wils., and F. berteroi (Mont.) C. Muell.. New Zealand J. Bot. 33: 291–299.

Pradhan, N. & Joshi, S.P. (2006). A checklist of Fissidens species (Musci: Fissidentaceae) of Nepal. Our Nature 4: 61–68.

Pursell, R.A. & Bruggeman-Nannenga, M.A. (2004). A revision of the infrageneric taxa of Fissidens. Bryologist 107: 1–20.

Suzuki, T. & Iwatsuki, Z. (2007). A new approach to the infrageneric classification of the genus Fissidens (Fissidentaceae, Bryopsida). Hikobia 15: 67–85.

Seppelt, R.D. & Stone, I.G. (2016). Australian Mosses Online 70. Fissidentaceae. Australian Biological Resources Study, Canberra. Version 16 June 2016. http://www.anbg.gov.au/abrs/Mosses_online/70_V2_Fissidentaceae.html

For more details about the history of this treatment see Fissidentaceae profile.