Hornschuch's Molendoa Moss

Molendoa hornschuchiana is known (R. H. Zander 1979b) from only one site in the flora area, in southern Alaska (Valdez Area, Chugach Mountains, between Delta Junction and Valdez, Keystone Canyon, alongside Hwy. 4, near Bridal Veil Falls). This distinctive species is the largest of the genus, with stems reaching several centimeters in European specimens seen, and perichaetial leaves to 3 mm. The Alaskan material lacks sporophytes but has lateral perichaetia. Worldwide, the species is disjunctive between mountainous areas with high annual precipitation in temperate climates.

Plants medium-sized to rather robust, (2.5–)4–5.5(–10) cm high, bright green to brownish green, in loose tufts. Stems erect, distantly branched, but densely foliate; central strand weakly differentiated. Leaves involute or weakly crisped when dry, erect-spreading when moist, narrowly to linear-lanceolate, 1.4–3.5 mm x 0.3–0.5 mm, sheathing at the base, gradually acuminate; margins nearly entire in the upper half, serrulate in the lower half; costa stout, percurrent to shortly excurrent; upper leaf cells irregularly rounded hexagonal to rounded quadrate, thick-walled, 7–19 µm x 6–16 µm, with several simple low papillae; basal cells oblong hexagonal to narrowly rectangular, 14–44 µm x 8–14 µm, usually smooth. Sporophytes terminal on later branches. Setae short; capsules obovoid; opercula with a long, oblique beak.

Stems to 2 cm, sclerodermis present. Leaves long-lanceolate, 3-4 mm, proximal shoulders denticulate by projecting corners of marginal cells, apex subulate; leaf base much widened, ovate-rectangular, sheathing the stem; costa excurrent as a mucro, semilunar in section at mid leaf, guide cells 4-9; distal laminal cells often longitudinally elongate medially, 1-2:1, rarely 2-stratose in patches.

Distribution: China, Russia, Europe, and northern Africa.

Habitat: usually on rocks; also on soil walls or ground in forests.

Molendoa hornschuchiana f. barbuloides Broth., Symb. Sin. 4: 29. 1929. Type. China: Sichuan, Yen-yuan Co., Handel-Mazzetti 2385 (lectotype H); Yunnan, Li-jiang Co., Handel-Mazzetti 4304 (syntype H). Molendoa hornschuchiana f. fragilis Gyoerffy in Broth., Symb. Sin. 4: 29. 1929. Type. China: Sichuan, Ning-yuen, Handel-Mazzetti 1406 (holotype H).

Hedwigia hornschuchiana Hooker, Musci Exot. 2: no. 103. 1819