Monographs Details: Cyathodium cavernarum Kunze
Authority: Bischler, Hélène, et al. 2005. Marchantiidae. Fl. Neotrop. Monogr. 97: 1--262. (Published by NYBG Press)
Synonyms:Cyathodium africanum Mitt., Cyathodium mexicanum Steph., Cyathodium barodae Chavan
Description:Species Description - Thallus green to yellowish green, delicate, small, dichotomously branched, in compact or discrete rosettes, fan-shaped, (2.2-)3.8-9.0 mm long, 0.7-2.2 mm wide; marginal cells chlorophyllose, rectangular to quadrate with outer walls slightly to strongly concave, oil cells triangular, devoid of chloroplasts. Dorsal epidermis delicate, chlorophyllose, cells (33-)45-60(-67) µm long, (20-)30-52(-60) µm wide, walls thin, lacking trigones; oil bodies light brown, l(-2), in idioblasts lacking chloroplasts, 15-27 mm long, 15-24 µm wide. Epidermal pores simple, smaller toward apex, wide open, slightly raised above epidermal cells, surrounded by 3-4(-5) concentric rows of 4-6(-10) elongate cells, the uppermost sometimes with sinuous, internally abutting cell walls. Ventral epidermis chlorophyllose, chloroplasts smaller than those of dorsal epidermis, cells polygonal, larger than those of dorsal layer, 90-187 µm long, (30-)45-67 µm wide. Midrib absent. Rhizoids abundant, long and colorless, of two types, large and ± straight-walled and narrower and sinuous, not tuberculate. Ventral scales near thallus apex and on ventral walls of involucre, simple, without appendages, filamentous to ± triangular deltoid, 3-6 cells long, with lateral or terminal cells containing an oil body. Monoecious. Antheridial receptacles lateral, sometimes occurring in close proximity of female receptacles, cushion-shaped to oblong-elliptical, 150-210 µm long, 142-230 µm wide. Involucres sac-shaped, divided into 2 lips, marginal cells elongate, reddish brown, in 1-2 rows with inner tangential walls thickened, mid-cells polygonal, thin-walled, brown on distal portion, hyaline below; archegonia 2-5 per involucre, maturation asynchronous. Sporophytes with a delicate seta of 6 uniseriate, narrow cells. Capsules ovoid, l(-3) per involucre, (0.2-)0.35-0.6 mm long, dark brown to black when mature, 1 cell thick; operculum of 2 tiers of cells, outermost 4(-8) cells, the innermost 8-12 cells; cells in upper 1/2-1/3 of capsule, below the operculum with annular to spiral thickenings, splitting into 4-6 irregular valves when drying, cells of lower half without thickening bands, nondehiscent, with chloroplasts and large oil bodies. Spores dark brown, (32-)35-54(-60) µm diam., densely to sparsely baculate-spinose, with rugose surface. Elaters (2-)4-16 per capsule, 390-585 µm long, 15-16 µm diam., varying in number with size of capsule, trispiral at middle, bispiral on the attenuated ends.

Discussion:Populations of C. cavernarum are quite variable in size of thallus, shape and size of pores, involucral and sporophyte position, size of sporophytes, number and size of spores, and number of elaters per capsule (Vital, 1974b). Thalli may be short and tumid to elongate and delicate. Plants growing on cement gutters along roadsides in Costa Rica are rather large in size, with thalli in tumid rosettes, deep green and with large pores. Populations on riverbanks tend to have more elongate, delicate thalli and less pronounced pores. In both variants the 2 rows of air chambers are distinctive. Involucral lips may be slightly to widely divergent, projecting beyond the rim of lobes, or located slightly below them, or at the same level. Sporophytes can be found deeply within the involucre or protruding at apex. Very small sporophytes (0.2 mm long) have been observed in lateral branches of thalli carrying large sporophytes (0.6 mm long) at apex. There may only be 2 or 3 elaters in the small capsules.

Cyathodium cavernarum closely resembles C. bischlerianum in its bright metallic-green color. It grows intermixed and usually above the latter species. The more robust, fan-shaped thallus with larger pores and air chambers in 2 rows, and the presence of an operculum, clearly distinguish C. cavernarum from C. bischlerianum. The thickenings of the upper capsule cells and spore ornamentation are also very different between the 2 species (see under C. bischlerianum).

Distribution and Ecology: Cyathodium caverna- rum has been collected in Mexico, C America (Costa Rica, Panama), the Caribbean (Cuba), and S America (Colombia and Brazil). It is the most widely distributed species of the genus and probably occurs throughout the Neotropics. In the Old World tropics the species has been reported from Africa, India, W and E Himalayas, Burma, and Indonesia (Java, Sri- vastava & Dixit, 1996). It grows in soil, on rocks, on eroded banks of rivers or creeks, along roadsides or trails, on bark of trees (palms and other angiosperms), on shaded sites, caves, on cement gutters and walls along roadsides, on cement flower pots. It grows on calcareous substrata but it can also be found on slightly acidic substrates where underlying bedrock is calcareous. In exposed habitats the species usually grows associated with members of the Pottiaceae; in ravines and riverbanks with species of Philonotis, Fis- sidens, Notothylas, Racopilum tomentosum (Hedw.) Brid., Cyathodium spruceanum, and Lejeuneaceae. Cyanobacteria are also closely associated with this and other species of Cyathodium, forming spherical colonies attached to various parts of the thallus

Distribution:Goiás Brazil South America| Mato Grosso Brazil South America| Minas Gerais Brazil South America| Ceará Brazil South America| Cuba South America| Colón Panamá Central America| Veracruz Mexico North America| México Mexico North America| Nayarit Mexico North America| Coclé Panamá Central America| Los Santos Panama Central America| Panamá Panama Central America| Alajuela Costa Rica Central America| Heredia Costa Rica Central America| San José Costa Rica Central America| Santiago de Cuba Cuba South America|