Monographs Details: Targionia
Bischler, Hélène, et al. 2005. Marchantiidae. Fl. Neotrop. Monogr. 97: 1--262. (Published by NYBG Press
Synonyms:Targionia hypophylla L.
Description:Genus Description - Thallus 1.5-4 mm wide, deep green to light green, often tinged with black-purple. Branching dichotomous and ventral. Epidermal pores simple, with 1-3 rings of 6-9 cells, radial walls thin or thickened. Air chambers in 1 layer, with chlorophyllose filaments. Oil cells numerous. Ventral scales in 2 rows, dark purple, with oil cells, marginal papillae, and a single large appendage. Asexual reproduction by specialized propagules lacking. Monoecious. Antheridia in irregular groups dorsal or terminal on main thallus, or on short ventral branches; scales associated with androecia lacking. Archegonia 1-10 per archegonial cluster, terminal in mussel-shaped involucre on ventral side of thallus apex. Involucre dark purplish, 4- to 8-layered; scales associated with gynoecia lacking. Calyptrae 3- to 4-layered after fertilization. Sporophytes 1-3 per involucre, with bulbous foot and hardly elongating seta. Capsules opening by an irregularly disintegrating lid and 5-8 irregular valves to 1/3 of capsule length; walls with annular thickenings. Spore/elater ratio 4:1. Spores ca. 3000 per capsule, 50-100 µm diam., proximal and distal faces with reticulate areoles and reticulate ridges, trilete scar distinct. Elaters with 2-3 helical bands. Gametophytic chromosome number n = 9 or 27.
Discussion:The genus Targionia is widely distributed in warm-temperate regions, between 55°N and 42°S. It is particularly frequent in Mediterranean-type climates and is absent in humid tropical lowland and arctic and boreal regions. The genus comprises 2 drought-tolerant species in the Neotropics, colonizing rock crevices and rock outcrops in areas with dry seasons. The 2 species have been attributed to distinct subgenera by Schuster (1992b): subgen. Targionia (Type. T. hypophylla L.) and subgen. Prototargionia R. M. Schust. (Type. T. stellaris (Mull. Frib.) Hässel).