Monographs Details: Cyathodium
Authority: Bischler, Hélène, et al. 2005. Marchantiidae. Fl. Neotrop. Monogr. 97: 1--262. (Published by NYBG Press)
Family:Targioniaceae
Scientific Name:Cyathodium
Synonyms:Cyathodium cavernarum Kunze
Description:Genus Description - Thallus 1-4(-16) mm wide, not tinged with purple. Branching dichotomous, ventral and apical; thalli forming often hemi-rosettes. Epidermis persistent. Epidermal pores simple, with 1 ring of 5-21 cells, without hyaline inner ring, wide open, radial walls thin. Air chambers in 1 layer, empty. Basal tissue reduced, in 0-2 layers, with or without oil cells. Rhizoids mostly smooth, some tuberculate, sinuous and with a spiral twisting. Ventral scales in 2 rows, often restricted to apical part of thallus, of 2-10 cells, with or without oil cells, with marginal papillae, sometimes with small, filiform appendage not constricted basally. Asexual reproduction in some species by "gemmae" (fragmenting thallus segments) from thallus margins or by ventral tubers. Monoecious or dioecious. Antheridia embedded in small ventral or apical branches with large scales. Archegonia 1-30, in archegonial cavity located ventrally beyond thallus apex. Archegonia terminal in bivalved involucre beyond thallus apex, sometimes bounded by thallus scales larger than those of sterile parts of thallus. Sporophytes with foot and hardly elongating seta. Calyptrae 2- to 4-layered after fertilization. Sporophytes 14 per involucre. Capsules opening by a lid and 6-8 irregular valves to 1/3-1/2 of capsule length, wall with annular thickenings in upper part only. Spore/elater ratio greater than 4:1. Spores 25 to more than 100 per capsule, 25-85 µm diam., proximal and distal faces tuberculate or short- to long-spinose, or with ± complete, tuberculate areoles and ridges, trilete scar hardly distinct. Elaters 4-100 per capsule, with 2-A helical bands. Gametophytic chromosome number n = 9.

Discussion:A genus of ca. 12 mesophytic-hygrophytic species able to grow under weak light intensities, found on rock, soil, or bark in forests, caves, along riverbanks, on rocks around waterfalls, on cement floors, stairs, and flower pots in humid areas, sometimes weedy in arable fields, distributed in the tropical belt in S Japan, S Africa, S America, C America, and the Caribbean at low elevations. The species are not drought-tolerant but are able to perennate with ventral tubers.

Srivastava & Dixit (1996) subdivided Cyathodium into 2 subgenera, subgen. Metacyathodium with ventral tissue several layers thick along the midline of the thallus, and subgen. Cyathodium with only a unistratose ventral epidermis below the air chambers.