Monographs Details: Plagiochasma intermedium Lindenb. & Gottsche
Authority: Bischler, Hélène, et al. 2005. Marchantiidae. Fl. Neotrop. Monogr. 97: 1--262. (Published by NYBG Press)
Family:Aytoniaceae
Synonyms:Ruppinia intermedia (Lindenb. & Gottsche) Trevis., Aytonia intermedia (Lindenb. & Gottsche) Underw.
Description:Species Description - Thallus 3.7-5 mm wide, yellowish green, often tinged with purple, with narrow, purplish margins; apical adventitious branches frequent. Epidermis smooth; epidermal cells (28-)35-40 × 21-24 |im, with small to medium-sized trigones. Epidermal pores 46-50 per mm2, raised above epidermis, 2428 µm diam., bounded by (2-)3-4 concentric rings of 8-9 cells, radial walls strongly thickened. Ventral scales purplish, with border of 1-2 rows of light red or hyaline, sinuose cells; appendages 2(-3), triangular, apex acute, with single cell or papilla apically, light red or purplish, as wide basally as in the center, 10-12 cells wide, not constricted but horizontally plicate basally, length/width ratio 2-2.5:1, margins partly bordered by smaller cells, without papillae. Male receptacle usually at base of apical adventitious branch, rarely dorsal, usually reniform, with ca. 30 antheridia. Scales of male and female receptacles hyaline or partly tinged with purple, acute, with single cell apically, margins with scattered papillae. Archegoniophores usually dorsal, rarely at base of apical adventitious branch, stalk 0.5-5.7 mm long, with thickened, dark purplish epidermal cells. Involucres 2-4, yellow, purplish, or brown. Spores 73-82 µm diam., light or dark brown, with complete or incomplete areoles on both faces, ridges tuberculate. Elaters without helical bands. Gametophytic chromosome number n = 9.

Discussion:Plagiochasma intermedium is the sole neotropical species having elaters without helical bands. Additionally, shape and structure of the appendages of the ventral scales separate the species from all other neotropical representatives of the genus.

Distribution and Ecology: The geographical range of P. intermedium is mainly neotropical and extends from 28°N to 10°N, including Mexico (Chiapas, Chihuahua, D. F., Jalisco, Mexico, Oaxaca, Puebla, San Luis Potosi, Veracruz), Guatemala, Costa Rica, and Venezuela (Aragua). The species has also been recorded from North Carolina (Schuster, 1992b). Records from other continents are erroneous and apply to other species. Plagiochasma intermedium is most common in C Mexico and Guatemala, rare elsewhere, and has been collected in dry, warm climatic areas in rock and wall crevices (lava or limestone), in exposed habitats or in open forests, between 800 m and 2300 m.

Distribution:Veracruz Mexico North America| San Luis Potosí Mexico North America| Distrito Federal Mexico North America| Chihuahua Mexico North America| México Mexico North America| Jalisco Mexico North America| Chiapas Mexico North America| Oaxaca Mexico North America| Puebla Mexico North America| Cartago Costa Rica Central America| San José Costa Rica Central America| Chimaltenango Guatemala Central America| Escuintla Guatemala Central America| Huehuetenango Guatemala Central America| San Marcos Guatemala Central America| Santa Rosa Guatemala Central America| Sololá Guatemala Central America| Aragua Venezuela South America|