Atrichum undulatum
Atrichum altecristatum
common smoothcap, common smoothcap moss, undulate atrichum moss
atrichum moss, wavy starburst moss
2–5 cm.
1–3 cm.
sparse below, more crowded above, 4–9 × 0.8–1.5 mm, lingulate to lanceolate, undulate, keeled distally, concave to flat proximally, with oblique rows of abaxial teeth on undulations, the apex acute;
costa percurrent, with teeth on abaxial surface in distal half;
lamellae 2–6, 2–4(–7) cells high;
median leaf cells 20–32 µm wide, irregularly angled to hexagonal, sometimes rounded, often transversely elongate, convex on both surfaces, smooth or with minute, verrucose or striate papillae on abaxial surface, walls firm, strongly collenchymatous with trigones.
2–8 × 0.7–1.5 mm, keeled and concave, rarely almost plane, rather narrowly lanceolate to lingulate, more or less undulate with rows of abaxial teeth on the undulations, the apex acute or sometimes proximal leaves obtuse;
costa percurrent or subpercurrent with abaxial teeth near apex;
lamellae 4–6(–8), laxly spreading, 4–6 (–9) cells high;
median leaf cells 24-28 µm wide, rounded to ± regularly hexagonal, rather thick-walled, strongly collenchymatous with trigones, smooth or occasionally with minute, verrucose or striate papillae mainly on abaxial surface.
1(–3) per perichaetium, 1–3 cm, reddish brown.
1–3 per perichaetium, 1–3.5 cm, erect.
polygamous, some shoots bisexual, others apparently male or female;
perigonial bracts broad, forming antheridial buds, often several buds per plant.
polygamous, some shoots apparently unisexual males or females, others with both sexes;
perigonia inconspicuous, the outer perigonial bracts resembling stem leaves but with a broader base, the inner small, ovate or suborbicular.
2–4(–8) × 0.5–1 mm, curved to distinctly arcuate, almost horizontal;
operculum 2–3 mm.
2–7 × 0.5–0.8 mm, cylindric, usually somewhat curved and inclined, sometimes straight and erect;
operculum 2–3 mm.
(12–)16–28 µm.
9–21 µm.
Atrichum undulatum
Atrichum altecristatum
No Atrichum species occurring in North America has been as widely misunderstood as A. undulatum. Evidently introduced from Europe, its weedy habitat and strongly arcuate, almost horizontal capsules are the surest means of recognition. Variety minus, a fixture of European manuals, is a stunted form that is highly variable and possibly a hybrid. Its occurrence in North America has not been demonstrated. As used by American authors (e.g., O. E. Jennings 1951), it probably refers to A. altecristatum.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Atrichum altecristatum is a common and widespread species, particularly in northcentral United States. It is distinguished from A. angustatum by the lamellae 4–6, and 4–6 cells high (against 6–9 lamellae, up to 15 cells high in A. angustatum), and leaf cells 24–28 µm in longest dimension, collenchymatous, with evident trigones (as opposed to cells smaller and subquadrate in A. angustatum, bulging mammillose on the adaxial surface). The difference in sexuality is more difficult to demonstrate, since most plants in a colony may appear female, with only a few shoots bearing a male inflorescence followed by a female inflorescence and sporophyte on the same stem about a centimeter above the male. As a result, the species is monoicous, but functionally dioicous. The taxon known as A. crispum var. molle (Holzinger) Frye evidently belongs here (R. R. Ireland 1969).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
BC
PNW Herbaria
WildflowerSearch
iNaturalist
USDA Plants Database
IL Wildflowers
KS Wildflowers
MD Biodiversity
MI Flora
MN Wildflowers
MO Plants
