Calostoma

The original genus description, based on the type species Calostoma cinnabarinum (synonymous with cinnabarina), was published by French botanist Nicaise Auguste Desvaux in 1809. The genus name Calostoma is derived from the Greek ' or "beauty", and ' () or "mouth"; similarly, several species are referred to in the vernacular as "prettymouths". In Korea, it is called Yongi, or "red cheeks". ==Description==

Fruit bodies, technically known as gasterocarps, form spherical spore-bearing heads with a peridium (outer tissue layer) made of two to four clearly defined layers of tissue. The outermost peridial layer is a thick gelatinous or shiny cuticle, which during maturity peels away to reveal the brightly colored peristome that has a star-shaped pore through which spores may escape. The innermost layer of the peridium is papery and membranous, and remains attached to the outer layers only at the apex of the star-shaped apical pore or slit. The fruit bodies may either have no stalk (sessile), or be atop a stalk. The stalk, made of thick, intertwined and fused cords of hyphae, is hygroscopic, and will expand upon absorbing moisture. The spore mass in the head, the gleba, is pale, and initially has thick-walled skeletal hyphae called capillitia. Clamp connections are present in the fungal hyphae. Spores The spores are spherical to elliptical in shape, and typically have surfaces that are reticulate (with interconnected grooves resembling a net) or pitted. The variations in the elaborate pitted-spore reticulations have inspired investigation with techniques such as scanning electron microscopy and atomic force microscopy. The latter technique was used to distinguish subtle details (at the nanometer scale) and differences in the fine structure of the spores of various Calostoma species. The spore reticulations have purpose: they become entangled and interwoven with nurse cells and scaly hyphae, the net effect of which is to prevent the spores from being blown away simultaneously. ==Development==

When grown in humid conditions, such as might typically be found in a temperate deciduous forest, Calostoma species develop a thicker, more gelatinous exoperidium (the outermost peridial layer). As the stalk expands, the exoperidium becomes sloughed off, exposing the endoperidium and a raised peristome—the ridge of tissue around the opening suggestive of the common name, "prettymouth". The exoperidium may help to protect the maturing gleba of late-fruiting species from harmful variations in temperature or humidity, or from insect predation. ==Habitat and distribution==

The species in Calostoma have been collected in regions of deciduous, temperate, tropical or subtropical forests, containing tree species from the families Fagaceae, Nothofagaceae, Myrtaceae, and Dipterocarpaceae. The type species C. cinnabarinum was shown to form ectomycorrhizae with Quercus species, using isotopic labeling, molecular and morphological analyses. Southeast Asian Calostoma have also been described as ectomycorrhizal. Calostoma sarasinii forms ectomycorrhizae with species of Lithocarpus (Fagaceae) while Calostoma retisporum forms ectomycorrhizae with species from the Myrtaceae. The ectomycorrhizal mode of nutrition is predominant in the Sclerodermatineae suborder. Historically, it had been assumed to be saprobic, due to its taxonomic uncertainty, and presumed relatedness to other saprobic fungi like the stalked puffballs and the earthstars. The distribution of the genus is limited to Australasia (Australia, New Zealand, Papua New Guinea), Southeast Asia, Asia, and North and Central America. Species have been described from Indonesia (Borneo, Java, Sumatra, New Guinea), Sri Lanka, Himalaya, Nepal, China, New Zealand, North America, and Latin America. Australian species include C. fuhreri, C. fuscum, C. insigne, C. rodwayi, and C. viride. David Arora mentions a preference for humid forests in eastern North America, particularly in the southern Appalachian Mountains. ==Uses==

Edibility In general, Calostoma species are not considered edible; because they typically begin their development underground, by the time fruit bodies appear they are too tough for consumption. However, a 2009 study reported that in the community of Tenango de Doria (Hidalgo state, Mexico), Calostoma cinnabarinum used to be collected by children and consumed "like a tidbit", although the tradition seems to have been abandoned in recent years. Locals called the young fruit bodies "yemitas"or “little yolks”. Biochemistry Calostoma cinnabarinum contains a pigment named calostomal that is responsible for its red color. The IUPAC name of this molecule is all-trans-16-oxohexadeca-2,4,6,8,10,12,14-heptaenoic acid. ==Species list==

The following species list is compiled from Index Fungorum as well as species published in the literature, but missing in Fungorum, specifically C. formosanum, C. junghuhnii, and C. sarasinii. The name listed under the species binomial is the authority—the author of the original description of that species, followed by the year of publication. ==References==