Polytrichastrum formosum
(2–)3–8(–20) cm, mostly unbranched.
6–8(–12) mm, erect to erect-spreading when dry, spreading to subsquarrose and broadly recurved when moist;
sheath ovate to elliptic, yellowish, hyaline-margined, gradually tapering or abruptly contracted to the blade, the cells at the shoulders forming a differentiated hinge;
blade lanceolate to linear;
costa prominent abaxially and toothed near the tip;
excurrent as a short, toothed point;
marginal lamina erect, (2–)3–5(–10) cells wide, plane or erect, sharply toothed from apex nearly to the sheath;
lamellae (3–)4–5(–7) cells high, margins ± entire to finely serrulate in profile, the marginal cells in section rounded to narrowly elliptic and somewhat taller than the cells beneath, the cell walls not or moderately thickened;
median cells of sheath 8–12 µm wide, narrowly rectangular, 5–7(–10):1;
cells of marginal lamina subquadrate, 10–15 µm. Sexual condition dioicous or polygamous;
perichaetial leaves similar to the foliage leaves, or somewhat longer, with a longer sheath.
3–6 cm, yellowish to reddish brown.
4–7 mm, rather slender or short-rectangular, acutely 4(–6)-angled, inclined to almost horizontal, pale yellowish brown to brownish;
hypophysis cylindric, indistinctly delimited or set off by a shallow groove;
exothecium smooth or the cells weakly convex, quadrate to hexagonal, without a central thin spot;
peristome 600 µm, divided to 0.6, the teeth 64 and highly regular in form or fewer and somewhat irregular, pale to brownish;
epiphragm absent marginal teeth.
12–16 µm.
Polytrichastrum formosum
Varieties 3 (2 in the flora).
European treatments often assert a similarity between Polytrichastrum formosum and Polytrichum commune, which cannot be said of the North American expression of the species. The habitat and ecology of the European plants are also distinct: A. J. E. Smith (2004) described P. formosum in Britain as a common and weedy species of heaths, moorland, woods, outcrops, and old walls.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
1. Plants often robust, 5-10(-20) cm; leaves subsquarrose and broadly spreading- recurved when moist; lamellae 5-7 cells high, entire, the marginal cells in section rounded, moderately thick-walled; capsule short rectangular; hypophysis delimited by a shallow groove; peristome teeth 64, regular in form; dioicous | var. formosum |
1. Plants rather slender, 3-6(-10) cm; leaves spreading when moist; lamellae (3-)4-6 cells high, the marginal cells narrowly elliptic, not or only slightly thickened; capsule slender; hypophysis not sharply delimited; peristome teeth 50-64, somewhat irregular in size and shape; monoicous (polyga- mous) | var. densifolium |
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