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[ Section Amanita page. ] [ Amanita Studies home. ] [ Keys & Checklist/Picturebooks ] Amanita siamensis R. Sanmee, Zhu L. Yang, P. Lumyong & S. Lumyong
Technical description (t.b.d.) BRIEF DESCRIPTION: The cap of A. siamensis is 75 - 95 mm wide, greenish yellow to olivaceous buff, grayish brown in the center, convex to plano-convex, with a low broad umbo, with a nonappendiculate and slightly down turned, striate margin (20 - 40% of radius). Volval remnants are present as cinnamon buff powdery or as floccose patches. The flesh is white and unchanged. The gills are free, white, crowded, with a farinose edge. The short gills are truncate to subtruncate. The stem is 90 - 150 × 10 - 15 mm, subcylindric or slightly narrowing upward, slightly expanded at the top, greenish yellow to olivaceous, and densely covered with cinnamon buff, farinose, squamules. The bulb is subglobose and 15 - 25 mm wide. The ring is membranous but easily broken during expansion, upper surface is white with fine radial striation, lower surface is cinnamon buff. Cinnamon buff volval material can be seen on the edge of the ring when viewed from above. The flesh is white. The spores measure (9.0-) 9.5 - 11.5 (-13.0) × (5.0-) 5.5 - 7.0 (-8.0) µm and are ellipsoid to elongate and inamyloid. Clamps are absent at base of basidia. This species is known only from Thailand from which it was described. It occurs in groups on the ground in forest dominated by trees of the beech family (Fagaceai). The authors compared the present species to east Asian and North American taxa. Among these were A. roseitincta (Murrill) Murrill, however, the present species lack the unusual and complex veil of A. roseitincta and is unlikely to be closely related. Other taxa to which they compare the present species are A. rufoferruginea Hongo, A. xerocybe Bas, and A. levistriata Dav. T. Jenkins. In general this species appears to belong to the group in section Amanita in which the skin of the cap is delayed in its separation from the volva. Hyphae intergrowing between the two tissues is common even up to maturity. This is one of the reasons why the powder on the cap persists so long, even through rain. Moreover this taxon belongs in the subgroup which lacks clamps and the further subgroup which bears brightly colored pigments. From all other known taxa, this species is separated by the proportionately narrow shape of its spores, the size and habit of the fruiting body, its set of pigments, and the marginal striation of the cap which is present from the beginning of expansion of the fruiting body. -- R. E. Tulloss and L. Possiel Photo: Rarunee Sanmee (holotype, Thailand) [ Section Amanita page. ] [ Amanita Studies home. ] [ Keys & Checklist/Picturebooks ] Last changed 6 June 2008. |
