Stegonia

Plants gregarious, bulbiform, white to whitish green distally, brown proximally. Stems to 3 mm; hyalodermis absent, sclerodermis absent, central strand present; axillary hairs ca. 3–6 cells in length, proximal 2 cells firm-walled. Leaves appressed when dry, appressed or loosely involute distally, weakly spreading when moist; nearly circular to very broadly ovate, sometimes elliptic, adaxial surface deeply concave, ca. 1.5–2 mm; base not differentiated, proximal margins not differentiated; distal margins broadly recurved to revolute, occasionally plane or weakly incurved, commonly serrulate near apex, occasionally entire, distal 1/4–1/3 of leaf usually hyaline, of rhomboid thick-walled cells; apex broadly acute or occasionally rounded; costa thin, excurrent as a flexuose hyaline awn or occasionally percurrent or subpercurrent, adaxial epidermal cells forming a bulging adaxial ridge, adaxial cells short-rectangular, bulliform (bulging, thin-walled), in ca. 3–4 rows, adaxial outgrowths rare, lamelliform, rounded or serrate and papillose; transverse section round, adaxial epidermis present, of bulliform cells, adaxial stereid band absent, guide cells 2 (often absent distally) in 1 layer, hydroid strand present, large (occasionally absent distally), abaxial stereid band present (occasionally substereid), round in section, abaxial epidermis absent distally, present proximally; proximal cells differentiated across leaf, rectangular, occasionally bulging, little differentiated or to 30 µm wide, to 4:1, walls of proximal cells often somewhat thicker than distal cells; distal medial cells rhomboid or hexagonal, grading to elongate rhomboid or hexagonal distally, often hyaline distally, 13–22 µm wide, 2–3:1, 1-stratose; papillae absent, cell walls usually thin medially and thick-walled near apex, especially on the abaxial superficial walls, convex on both sides. Specialized asexual reproduction absent. Sexual condition monoicous (paroicous or autoicous); perichaetia terminal, interior leaves little differentiated. Seta 0.2–1.2 cm or very short (70–100 µm). Capsule stegocarpous or cleistocarpous, theca exerted, ovate-cylindric and often slightly curved, to 1–2 mm; or immersed, ovate and very shortly apiculate, ca. 0.7 mm, annulus absent or of 2–3 rows of persistent, vesiculose cells; operculum absent or short-rostrate; peristome teeth absent, rudimentary or 16, cleft to near base, occasionally perforate, ligulate, straight, to 125 µm. Calyptra cucullate. Spores 20–45 µm. KOH distal laminal color reaction yellow.

Distribution

w North America, Mexico, Europe, Asia, Africa, Antarctic.

Discussion

Species 3 (2 in the flora).

The capsules of Stegonia exhibit a reduction series (R. H. Zander 1993): one species is peristomate, another cleistocarpous, while the third, of northern Africa, is stegocarpous but eperistomate. Both species in the flora area have perichaetial leaves with a leaf apex of hyaline, elongate, rectangular cells (this variable in S. latifolia) similar to that of the arctic Hilpertia velenovskyi, but smaller, proximal leaves similar to those of Tortula acaulon.

Selected References

None.

Lower Taxa

Stegonia hyalinotricha, Stegonia latifolia

Key

1	Seta (2-)4-12 mm; capsule stegocarpous, exerted, ovate-cylindric, to 1-2 mm.	Stegonia latifolia
1	Seta 0.07-0.1 mm; capsule cleistocarpous, immersed, ovate, ca. 0.7 mm.	Stegonia hyalinotricha