Plagiochasma cuneatum A.Evans
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Authority
Bischler, Hélène, et al. 2005. Marchantiidae. Fl. Neotrop. Monogr. 97: 1--262. (Published by NYBG Press)
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Family
Aytoniaceae
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Scientific Name
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Type
Type. U.S.A. Texas: Hamilton s Pool, Feb 1931, McAllister s.n. (holotype, YU).
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Synonyms
Plagiochasma elongatum (Lindenb. & Gottsche) Trevis.
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Description
Species Description - Thallus 3-4 mm wide, light or yellowish green with narrow, purplish margin; apical adventitious branches frequent, often short. Epidermis finely granulose; epidermal cells 28-35 × 21-24 µm, with medium-sized or large, often nodulose trigones. Epidermal pores 15-20 per mm2, raised above epidermis, usually 28-35 Jim diam., bounded by (2-) 3(-4) concentric rings of (7-)8(-9) cells with strongly thickened radial walls. Ventral scales purplish or dark red, with border of 1-2 rows of light-red or hyaline, sinuose cells; appendages usually 2-3, narrowly triangular, apex acuminate, with row of 3-4 cells apically, hyaline, contrasting with the dark scale body, widest basally, 10-14 cells wide, not constricted or plicate, length/width ratio 4-5:1, margins not differentiated, sometimes with some teeth and papillae. Male receptacle dorsal or at base of apical adventitious branch, usually reniform, with 20-30 antheridia. Scales of male and female receptacles hyaline or purplish, or partly tinged with purple, acuminate, with row of 3-5 cells apically, margins with scattered papillae. Archegoniophores dorsal or at base of apical adventitious branch, stalk 2.3-4 mm long, with thickened, dark-red epidermal cells. Involucres 2-3, light brown or purplish. Spores 94-118 µm diam., light or dark brown, both faces areolate, areoles and ridges tuberculate. Elaters with 2-3 helical bands. Gametophytic chromosome number n = 9.
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Discussion
Plagiochasma cuneatum is easily distinguished by the finely granulose epidermis and by its dark purplish ventral scales with long, acuminate, hyaline appendages.
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Distribution
The range of the species extends from 30°N to 15°N, from the U.S.A. (Texas), Mexico (D. F., Mexico, Nuevo Leon, Veracruz), Guatemala to Haiti. It is infrequent everywhere and has been collected in rock crevices of calcareous rocks or sandstone, in dry, warm climatic areas, from sea level to 2300 m.
Haiti South America| Veracruz Mexico North America| Distrito Federal Mexico North America| México Mexico North America| Nuevo León Mexico North America| Huehuetenango Guatemala Central America| Ouest Haiti South America|