Monographs Details: Plagiochasma jamaicense (Haynes) A.Evans
Authority: Bischler, Hélène, et al. 2005. Marchantiidae. Fl. Neotrop. Monogr. 97: 1--262. (Published by NYBG Press)
Family:Aytoniaceae
Synonyms:Aytonia jamaicensis Haynes
Description:Species Description - Thallus 4.3-6.7 mm wide, light or yellowish green, with narrow, purplish margins; apical adventitious branches frequent. Epidermis smooth; epidermal cells 35-47 × 24-28 µm, with medium-sized or large, sometimes nodulose trigones. Epidermal pores 10-35 per mm2, raised above epidermis, 14-17 µm diam., bounded by 3(-4) concentric rings of (6-)8 cells, radial walls hardly thickened. Ventral scales purplish, with border of 2-3 rows of light-red or hyaline, sinuose cells; appendage l(-2), triangular, apex acute, with row of (1-)2-3 cells apically, light red or purplish, widest basally, 8-10 cells wide, constricted and horizontally plicate, length/width ratio 1.5-2:1; margins bordered by 1-2 rows of smaller cells, some with papillae. Male receptacle at base of apical adventitious branches, reniform, with 20-30 antheridia. Scales of male and female receptacles hyaline or purplish, or partly tinged with purple, acute, with row of 2-3 cells apically, margins with scattered papillae. Archegoniophores dorsal, stalk 4-6 mm long, with slightly thickened, dark-purplish epidermal cells. Involucres 1-4, yellowish or tinged with purple. Spores 82-94 Jim diam., dark yellow or brown, with complete areoles on both faces, ridges tuberculate. Elaters with 2(-3) helical bands. Gametophytic chromosome number unknown.

Discussion:Plagiochasma jamaicense is related to P. wrightii and can be distinguished from the latter species by the larger thallus, finely granulose epidermis, longer epidermal cells, and smaller epidermal pores, less raised above the thallus surface. Moreover, the appendages of the scales are smaller and light red or purplish in color.
Distribution:Jamaica South America| Distrito Federal Mexico North America|