Fissidens integerrimus

Detailed description

Plants medium sized for the genus, saxicolous, rheophytic, dark green; all but youngest leaves usually encrusted with diatoms and detritus; shoots forming dense smooth mats of parallel prostrate stems in fast flowing water, more sparsely gregarious with more or less erect stems in slower moving water, falcate, 5-15 mm long, up to 2 mm wide, frequently branched; shoot branches readily detached; rhizoids at base of shoots and base of shoot branches, occasionally in leaf axils; stems with central strand, small axillary hyaline nodules differentiated, uniseriate axillary hairs present; leaves in 10-45 pairs, when moist slightly falcate, when dry little altered, mid-stem leaves slightly overlapping to distant, oblong lanceolate, 1.25- 2 mm long, 0.25-0.35 mm wide; leaf apex obtuse to acute; vaginant lamina 1/2-2/3 of leaf length, junction only along nerve or up to mid-way across lamina; dorsal lamina narrow, reaching to stem; nerve curved below, bent at apex of vaginant lamina, failing before leaf apex, surface cells with small lumina in cross-section, deuter cells exposed on the adaxial face; leaf margins serrulate; intramarginal border usually well developed in proximal half of vaginant lamina but sometimes very weak or absent, distal half of vaginant lamina unbordered; laminae unistratose; cells of apical and dorsal laminae quadrate to hexagonal, thick-walled (8-) 11-16(-20) microns long, clear, smooth, those in 1-4 marginal rows smaller than those nearer the nerve. Apparently dioicous or cladautoicous; female inflorescences terminal on main and axillary stems; perichaetial leaves narrower than vegetative leaves; archegonia 300-350 microns long; setae 2.5-3.5 mm long; capsule inclined, symmetrical, urn 0.4-0.6 mm long, exothecial cells quadrate to short rectangular, numbering about 30 around perimeter at midcapsule; operculum rostrate with an erect beak, equaling the length of the urn; peristome teeth 50-60 microns wide at base, bifurcate from below mid-tooth, lamellae ornamented with closely packed smooth ridges bearing intramural papilla-like thickenings in basal part of tooth, smooth at the zone of bifurcation, filaments spirally thickened; spores 13-20 microns; calyptra slightly scabrous above, mitriform, not completely covering operculum.