5. Zygodon viridissimus (Dickson) Bridel, Bryol. Univ. 1: 592. 1826.
Bryum viridissimum Dickson, Fasc. Pl. Crypt. Brit. 4: 9, plate 10, fig. 18. 1801
Plants to 2.3 cm. Stem leaves loosely erect and ± spirally twisted to somewhat contorted, sometimes falcate-secund at stem apices when dry, erect-spreading to spreading when moist, lanceolate, narrowly so, elongate-lanceolate, oblong-lanceolate, or linear-lanceolate, 1-2 mm; margins entire or irregularly serrulate or serrate near apex, somewhat wavy; apex acute with gradual apiculus, apiculate, short-apiculate, or short-acuminate; costa ending below apex, abaxial surface covered by quadrate papillose cells distally; basal laminal cells subquadrate to rectangular; distal cells 7-11 µm, papillae 2-4 per cell, walls somewhat thick. Specialized asexual reproduction by clavate, elliptic, or subcylindric gemmae, longitudinal walls present or absent. Sexual condition dioicous. Sporophytes unknown.
Varieties 5 (3 in the flora): North America, Mexico, Central America, Europe, w Asia, Africa, Atlantic Islands (Canary Islands).
Zygodon viridissimus in the flora area includes phenotypes with ovate to elliptic gemmae; narrowly lanceolate, loosely erect leaves; the abaxial surface of the distal 1/3-1/2 of the costa covered with papillose, quadrate cells; dioicous sexual condition; and rudimentary (or no) peristome.