Zygodon viridissimus (Dicks.) Brid.

Authority

Sharp, Aaron J., et al. 1994. The Moss Flora of Mexico. Part Two: Orthotrichales to Polytrichales. Mem. New York Bot. Gard. 69 (2)

Family

Orthotrichaceae

Scientific Name

Zygodon viridissimus (Dicks.) Brid.

Description

Species Description - Plants up to 2.3 cm high (usually less than 1 cm), yellowto dark-green, not or somewhat tomentose below, forming loose mats. Stems simple or not much branched. Brood bodies occasional, ovoid to elliptic, with 2-4 horizontal septa and sometimes longitudinal septa. Leaves loosely erect-imbricate, somewhat twisted, and sometimes ± slightly falcate-secund (the tips bent less than 90°) in the upper portions of stems when dry, erect-spreading to spreading-recurved when moist, ± keeled below, 0.5-2 mm long, oblong-lanceolate, lanceolate, or linear-lanceolate, acute to broadly acuminate, sometimes with a ± gradual apiculus, not much decurrent; margins plane or broadly reflexed below, sometimes ± wavy, entire or rarely with 1-2 small teeth near the apex; costa ending below the apex, the back of the upper 1/3 to 1/2 covered with quadrate, papillose cells; upper cells 7-12 µm, irregularly rounded to hexagonal-quadrate, moderately thick-walled, densely papillose, with (1-)2-5 small, rounded papillae per cell; basal cells pale-yellow to hyaline, smooth, subquadrate to rectangular. Dioicous. Setae 2-7(-9) mm long; capsules 1-2.1 mm long, narrowly ovoid to fusiform, 8-ribbed ± the entire length, yellow-brown, gradually contracted to the setae through a long neck; operculum long-rostrate; exothecial cells slightly differentiated in bands; peristome none or consisting of a low, papillose membrane. Spores 11-15 µm, papillose. Calyptrae smooth, cucullate, naked.

Discussion

Fig. 453a-g

Z. viridissimus (Dicks.) Brid., Bryol. Univ. 1: 592. 1826.

Bryum viridissimumDicks., Pl. Crypt. Brit. 4: 9. 1801.

Zygodon viridissimus, as broadly delimited, includes Northern Hemisphere phenotypes with ovoid to elhpsoidal brood bodies; narrowly lanceolate, more or less straight leaves; back surface of the costa covered with papillose, quadrate cells in the upper 1/3 to 1/2; dioicous sexuality; and no peristome. Zygodon ehrenbergii is, in general, larger, with more twisted-curved leaves m o r e strongly keeled above, usually with a few leaves in each population sparsely toothed just below the apex.

In Mexico, all collections (except one) have brood bodies with both longitudinal and horizontal septa and more or less entire leaf margins and can be referred to the var. viridissimus. The var. rupestris Lindb. ex C. J. Hartm., with entire leaf margins and brood bodies lacking longitudinal septa, is known from Los Angeles Co., California. A specimen from Baja California Sur (Bowers et al. 5153f, TENN) is similar, but the material is scant and only a few brood bodies, possibly immature, are present. Further collections are needed to verify the occurrence ofthe variety in western Mexico.

Distribution

Most frequently on trunks of Quercus, but also on Pinus and Abies, occasionally on rock faces, at 2000-3900 m elev.; Baja California Sur, Chiapas, Chihuahua, Durango, Hidalgo, Jalisco, Mexico, Michoacan, Nayarit, Oaxaca, Puebla, Tamaulipas, Veracruz.—Mexico; Guatemala; Dominican Republic; generally rare and sporadic in distribution, with disjunct populations in Arizona, New Mexico and Appalachian Mountains, as well as Nova Scotia, New York, Massachusetts, Ontario, Quebec, Michigan, Wisconsin,

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