Fissidens Moss

Fissidens subbasilaris is distinguished, even in the field, by a costa obscured by chlorophyllose cells distally, and short perichaetial branches in the axils of proximal leaves. The plants are typically dark-green and often tinged with red.

Plants to 12 × 1.5-3.5 mm. Stem branched; axillary hyaline nodules absent; central strand present. Leaves as many as 28 pairs, sometimes ± undulate, oblong, obtuse-apiculate to acute, to 2.4 × 0.3-0.4 mm; dorsal lamina narrowed proximally, ending before or at insertion; vaginant laminae ¹/2-²/3 leaf length, acute, ± unequal, minor lamina ending near margin; margin evenly crenulate-serrulate but irregularly serrate distally; costa ending 6-16 cells before apex, covered and obscured above by chlorophyllose cells, taxifolius-type; lamina cells irregularly 2-stratose, smooth, bulging, firm-walled, irregularly rounded-hexagonal, 7.5-10 µm. Sexual condition gonioautoicous and cladautoicous; perigonia gemmiform, axillary, and on short branches; perichaetia on short axillary branches near proximal ends of stem. Sporophytes 1 per perichaetium. Seta 1.5-5.5 mm. Capsule theca 0.8-2.1 mm, erect, radially symmetric or nearly so; peristome taxifolius-type; operculum long rostrate, 0.6-0.9 mm. Calyptra cucullate, smooth, 1.5 mm. Spores 13-18 µm.

Fissidens subbasilaris Hedw. Sp. Muse. 155. 1801
Plants smaU, 5-10 mm. high, scattered to closely gregarious, erect or ascending; stems simple or branching; leaves 10-18 pairs, somewhat crispate when dry, close and overlapping, reachmg 1-1.5 mm. in length, oblong, obtuse, or subacute and apiculate by a projecting cell, those in the middle of the stem usuaUy the largest, minutely and evenly crenulate below by projecting ceU-angles, minutely and irregularly serrulate above by larger ceUs, without border, the costa strong, covered and obscured with mamiUose cells in the upper part, ending several cells below the apex; vaginant laminae reaching about half the length of the leaf; dorsal lamina usuaUy ending abruptly before or after reaching the stem; leaf-ceUs rather obscure, 7-10 ^ in the upper middle of the leaf, strongly and bluntly mamiUose on both sides, irregularly roimdedhexagonal, incrassate, larger and less obscure in the base of the vaginant laminae; dioicous; sporophj^e arising from a leaf-axil near base of stem; seta 3-5 mm. long, reaching about to the top of the stem; capsule oblong-cylindric, erect and symmetric or slightly curved, brown, the urn rather more than 1 mm. long, the exothecial ceUs scarcely coUenchymatous ; operculum conic-rostrate, about half the length of the urn; peristometeeth nodulose above, not spiraUy thickened or papiUose; spores 16-18 m in diameter, maturing in autumn.
Type locality: Near Ivancaster, Pennsylvania {Muhlenberg) .
Distribution: On soil, stones, and base of trees; Ontario and Connecticut, southward to the Gulf east of the Mississippi; common on bases of trees in Florida, but fruiting sparingly.