Cyathus helenae or Helena's bird's nest is a species of fungus in the genus Cyathus, family Nidulariaceae. Like other members of the Nidulariaceae, C. helenae resembles a tiny bird's nest filled with 'eggs'—spore-containing structures known as peridioles. It was initially described by mycologist Harold Brodie in 1965, who found it growing on mountain scree in Alberta, Canada. C. helenae'''s life cycle allows it to reproduce both sexually and asexually. One of the smaller species of Cyathus, C. helenae produces a number of chemically unique diterpenoid molecules known as cyathins. The specific epithet of this species was given by Brodie in tribute to his late wife Helen. Description The resemblance that Cyathus helenae bears to a miniature bird's nest with eggs is the source for its common name, bird's nest fungi. The fruit body, or peridium, of C. helenae is obconic, that is, shaped roughly like an inverted cone. The upper third of the peridium is flared outwards sharply, and the opening is normally 5–6 mm wide, while the height of the fruit body is 7 mm. The outer surface of the peridium, the ectoperidium, is pale brown to grey in color, and covered with clusters of fungal hyphae that resemble hairs. These hairs appear to be aggregated into clusters ("nodular"), and generally point downward. The inner surface of the peridium, the endoperidium, is smooth with a grey to silver and somewhat shiny surface. This inner surface also has faint but distinct vertical ridges, known as plications. Like many other Cyathus species, the cup is attached to its growing surface by a clump of mycelium called an emplacement; in C. helenae the diameter of the emplacement is typically wider than that of the peridium, and it often incorporates bits of "organic trash". The 'eggs' of the bird's nest – the peridioles – are 2 mm in diameter, and covered with a silvery tunica (the outermost covering layer of the periodiole). Peridioles are attached to the fruit body by a funiculus, a structure of hyphae that is differentiated into three regions: the basal piece, which attaches it to the inner wall of the peridium, the middle piece, and an upper sheath, called the purse, connected to the lower surface of the peridiole. In the purse and middle piece is a coiled thread of interwoven hyphae called the funicular cord, attached at one end to the peridiole and at the other end to