Schistidium apocarpum
Schistidium agassizii
schistidium moss
agassiz's schistidium moss, water grimmia, water schistidium
1.2–12 cm, central strand weak or absent.
(0.9–)1.3–2.5(–5) cm, central strand absent or indistinct.
erect or curved, rarely (falcate-) secund when dry, ovate-lanceolate, sharply keeled distally, (1.3–)1.7–2.5(–3.2) mm, 1-stratose or rarely 2-stratose in striae distally;
margins usually recurved throughout or to just before the apex, usually denticulate distally, 1 or 2-stratose;
apices acute or sub-obtuse;
costa percurrent or excurrent as a smooth or weakly denticulate, occasionally decurrent awn, abaxial surface often papillose;
basal marginal cells usually quadrate;
distal laminal cells mostly short-rectangular, 8–10 µm wide, smooth, sinuose.
erect or curved, often toward stem, sometimes contorted when dry, linear-lanceolate to ligulate, sometimes oblong-lanceolate, weakly keeled or concave proximally, usually nearly flat distally, sometimes concave or rarely weakly keeled, 1–3.5 mm, 1-stratose;
margins plane or weakly recurved proximally, plane, rarely incurved distally, smooth or weakly crenulate, sometimes eroded distally, usually 1-stratose, occasionally partly 2-stratose;
apices obtuse or acute, sometimes ending in a hyaline cell;
costa sub-percurrent or percurrent, awn absent, smooth;
basal marginal cells short-rectangular or quadrate;
distal laminal cells quadrate or short-rectangular, often rounded, (7–)9–12 µm wide, smooth, weakly sinuose.
autoicous.
autoicous.
dark red or brown, short-cylindric, 0.7–1.3 mm;
exothecial cells usually quadrate, sometimes mixed with short-elongate or oblate cells, thin-walled, usually trigonous;
stomata present;
peristome patent or erect, often twisted, 350–600(–700) µm, red, densely papillose, usually perforated.
light brown, rarely almost black, campanulate, rarely cupulate, 0.8–1.2(–1.5) mm;
exothecial cells isodiametric or slightly elongate, often round or irregularly angular, walls thick, often somewhat curved, trigonous;
rim darker than capsule wall, sometimes red;
stomata absent;
peristome squarrose to revolute, 350–570 µm, red or orange-red, finely papillose, moderately to strongly perforated.
11–14(–19) µm, granulose or smooth.
10–18(–25) µm, smooth or granulose.
Schistidium apocarpum
Schistidium agassizii
Although H. H. Blom (1996) considered Schistidium apocarpum to be restricted in the flora area to the eastern portions of North America, it is more widespread and scattered across the continent. The denticulate leaf margins, papillose abaxial costal surface, short-cylindrical capsules, and the thin-walled, often evenly quadrate exothecial cells are distinguishing characters. The long peristome teeth are also useful in identifying S. apocarpum. In good condition the peristome can only be confused with that of S. trichodon, which differs in the darker, often black color of its plants, the peristome teeth often forming a dome, and the cylindrical capsules that retain the columella.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Schistidium agassizii is sometimes confused with S. rivulare, another dark species found along watercourses. It differs in having linear-lanceolate, almost straight-sided, and distally nearly flat leaves, with plane or weakly recurved margins. The leaves of S. rivulare are often lighter in color, ovate-lanceolate to ovate-triangular, and always distally keeled with recurved margins. Also, S. rivulare usually forms much larger patches than does S. agassizii. New leaves of S. agassizii are often yellow-green or brownish, somewhat concave-keeled distally, and are somewhat julaceous, forming finger-like projections at the tips of stems. Schistidium subjulaceum is another similar species that grows along watercourses but is distinguished from S. agassizii by the same vegetative characters that separate the latter from S. rivulare, as well as by its smaller, often lighter colored, and short-cylindrical or ovoid capsules.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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