Schistidium apocarpum
Schistidium heterophyllum
schistidium moss
schistidium moss
1.2–12 cm, central strand weak or absent.
1–2.5(–4) cm, central strand distinct.
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, rarely curved, usually imbricate when dry, ovate-lanceolate to ovate-triangular, keeled distally, concave proximally, (0.8)–1.6–2.4(–3) mm, 2-stratose distally;
margins plane or erect, sometimes incurved, smooth, 1-stratose or 2-stratose;
apices acute or somewhat obtuse;
costa usually excurrent as a spinulose-denticulate or nearly smooth, usually straight, often very long decurrent awn, smooth;
basal marginal cells short-rectangular or quadrate, sometimes with transverse walls thicker than longitudinal walls, trigonous;
distal cells quadrate, ovate, or short-rectangular, 5–6(–8) µm wide, smooth, straight or weakly sinuose.
autoicous.
dioicous.
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.
dark reddish brown, short-cylindric or cupulate, 0.8–1.1 mm;
exothecial cells isodiametric or oblate, usually thin-walled;
stomata present;
peristome patent, 350–550 µm, red, finely papillose, strongly perforated.
11–14(–19) µm, granulose or smooth.
10–13 µm, finely papillose.
Schistidium apocarpum
Schistidium heterophyllum
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.)
The imbricate, concave, and long-awned leaves (the concentration of awns at growing tips of the branches resemble brushes), with plane or erect margins and 2-stratose distal laminae, along with the ease by which patches fragment into individual stems, make Schistidium heterophyllum, in most cases, an easily recognized species, even though it is usually sterile. Schistidium tenerum is similar in most of these characters, but is much smaller and usually forms more compact cushions. Also, its distal laminae are unevenly 2-stratose, its leaf margins are recurved, and its awns are often strongly flexuose when dry. Where their ranges overlap in arid regions of western North America, S. heterophyllum can be easily mistaken for the macroscopically similar Grimmia laevigata. Both species are usually sterile, are of the same coloration and size, and have similar leaf characteristics. These taxa can be separated by a number of characters: the costa is pronounced on the abaxial leaf surface of S. heterophyllum and forms a distinct ridge, whereas the costa of G. laevigata is flat or only weakly raised above the laminal surface, its leaves are usually broader and not as imbricate when dry, its distal leaf cells are wider (7–9) than those of S. heterophyllum (5–6), and its leaves usually narrow considerably more to the stem base than do those of S. heterophyllum.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
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