Fissidens Moss (Fissidens ventricosus)

Description

Plants rich grass-green to rather deep green, to 30 mm high, with up to 20 pairs of leaves. Leaves, when dry, irregularly wrinkled; when moist, spreading from stem at about a 30 degree angle, to 3.5 mm long, 2.5-3: 1 oblong to oblong lingulate. Vaginant lamina to 4:1, extending about 1/2 of leaf, the two sides converging at an acute angle, homostichous. Dorsal lamina narrowed but present to insertion with the limbidium strong even at insertion. Median cells of apical and dorsal laminae not in regular rows, unistratose or with bistratose streaks, smooth, to 14 -m wide, thick-walled with lumen: wall ratio about 3-4: 1, hexagonal to rhomboidal with angular lumens and no corner thickenings. Median cells of vaginant lamina in somewhat regular rows, isodiametric, only slightly larger than cells of dorsal lamina. Basal juxtacostal cells somewhat larger and more elongate. Costa to 400 -m at base, percurrent to subpercurrent, sometimes merging with limbidium at apex and forming an apiculus. Margin plane, entire throughout or with a few small teeth near apex. Limbidium strong throughout, confluent at apex with costa or ending several cells below apex, up to 8 cells wide, formed entirely of hyaline and very thick-walled stereids, minutely or not at all decurrent on dorsal lamina. Stem with no central strand and with a strong, often reddened stereome to 4 cells thick, only gradually differentiated from 3-5 layers of enlarged, thin-walled inner corticals; lateral cells of outer cortex poorly differentiated. Axillary hyaline nodules not present. Axillary hairs 125-200 -m, of 2-3 cells with basal cell pale to light brown, up to 8 times as long as broad. Rhizoids red-brown, fascicled in axils of lower leaves, monopodial, to 10 -m at insertion. Dioicous. Perichaetia and perigonia terminal with seta barely exserted, to 8 mm, red-brown, nearly straight, smooth and rigid. Urn to 1 mm long, oblong and symmetrical, about 2: 1. Operculum conic, 1/4-1/3 as long as urn. Calyptra cucullate, smooth. Peristome reddish-brown, to 250 -m long, minutely papillose proximally, spirally ridged distally. Exothecial cells in regular vertical rows, somewhat bulging on outer surface, mostly isodiametric with angular lumens, rather thin-walled, to 15 -m wide. Spores spherical to elliptic, to 25 -m, nearly smooth.