Cystodermella cinnabarina

The species was first described as Agaricus granulosus var. cinnabarinus by German botanist Johannes Baptista von Albertini and the American Lewis David de Schweinitz in 1805.^[2] The species has also been known variously as Agaricus terreyi (Berkeley and Broome, 1870),^[3] Armillaria cinnabarina (Kauffman, 1922),^[4] Lepiota cinnabarina (Karsten, 1914),^[5] and Cystoderma terreyi (Harmaja, 1978).^[6]

The cap is hemispherical in shape at first, becoming convex and finally flat with maturity, and up to 5.5 cm (2.2 in) wide.^[7] The cap cuticle is cinnabar, brick-red or rusty orange and densely covered with fine granules. The flesh is white to pallid, with a mild to sweet taste and mild to mealy smell.^[7] The gills are white to cream, dense and emarginate or adnate. A finely cottony partial veil covers the gills in immature specimens, tearing away to leave behind a delicate ring. The stem is white above the ring, and scaly below, with dark orange squamules. The stem is up to 6 cm (2.4 in) tall^[7] and 1.5 cm (0.6 in) in diameter, sometimes bulbous in the base and hollow.

The basidiospores are oval, hyaline, and non-amyloid, with dimensions of 3.5–5 by 2.5–3.5 μm. The spore print is white.^[8][9] The basidia (spore-producing cells) are club-shaped, and 17–24 by 4–5 μm. C. cinnabarina always has cells called cheilocystidia—cystidia that are present on the edges of gills, which in this species are spear-shaped. This microscopic feature may be used to help distinguish it from the similar-coloured C. adnatifolia^[10] and C. granulosa, which also bear non-amyloid spores, but lack cystidia.^[9]

Species of Cystoderma (including orange-capped species such as Cystoderma amianthinum) have amyloid spores, in comparison to non-amyloid spores in C. cinnabarina and species of Cystodermella in general. This is determined by staining tissue with chemicals in the amyloid reaction—all Cystodermella species show a negative reaction (spores remaining colourless).^[11]