Pseudotaxiphyllum Moss

Pseudotaxiphyllum homomallifolium

Pseudotaxiphyllum homomallifolium (Redf.) Ireland, Caldasia 16(78): 267. 1991. Isopterygium homomallifolium

Redf., Bryologist 76: 440. 1973. Type: Texas, Kimble Co., along North Llano River, ˜½ mi. S of Roosevelt, Redfearn 27170 (holotype: NY!; isotype: MICH!).

Plants in thin to dense mats, glossy, yellowish green. Stems to 1.5 cm long, 1–2 mm wide, simple or irregularly branched. Asexual reproductive bodies lacking. Leaves 0.8–1.2 mm long, 0.3–0.5 mm wide, semiflaccid to rigid, distant to close and overlapping, erect-spreading, sometimes upturned-homomallous, occasionally complanate, smooth, lanceolate to ovate-lanceolate, symmetric, long-acuminate; margins plane, serrulate nearly to base; costa weak, short and double or lacking; median cells 60–120 × 5–9 µm, smooth; apical cells smooth; alar cells poorly differentiated,

a few short-rectangular cells often present. Sporophytes not seen on Latin American plants. North American plants reported (Ireland, In press a) to be autoicous. Setae 0.8–1.6 cm long, yellow to reddish; capsules 1.4–1.7 mm long, erect to horizontal, slightly cernuous, ellipsoid, contracted below the mouth when dry; operculum high-conic, 0.4–0.6 mm long, high-conic to short-rostrate; annulus present, deciduous, of 2–3 rows of cells. Spores 9–16 µm in diameter.

Distribution and ecology: Rare; known in Latin America only from the state of Sonora, Mexico (Figure 27); occurring on rocks and under rock ledges, 1350–1875 m; also known to occur in the southwestern United States (Arizona, New Mexico, and Texas).

Discussion: Pseudotaxiphyllum homomallifolium is distinctive because of its long-acuminate, upturned-homomallous leaves with serrulate margins, its broad median leaf cells, its few differentiated cells in the alar regions, and its autoicous sexual condition.

Although foliose pseudoparaphyllia were attributed to P. homomallifolium when Redfearn (1973) described the species, we do not believe they should be classified as such structures. The multicellular structures rarely found on the stems seem to be part of a developing branch primordium. They do not appear to be distinctly separated from the rest of the primordium, sometimes not even evident on the stems at the bases of mature branches like typical pseudoparaphyllia.

Specimens examined: MEXICO. Sonora: Loop of the Río de Bavispe, cerro del Capulin, NW of Aribabi, 1875 m, Harvey 1704 (MICH); Cañon de Huépari, N of Aribabi, 1350 m, Harvey 1747 (MICH).