Sirobasidium magnum Boed, Bulletin du Jardin Botanique Buitenzorg, III, 13: 267. 1934.
Description：
Basidiocarps foliose, lobato-gyrose, gelatinous, light brown to reddish brown, 1-4 cm ø, always associated with Hypoxylon sp. Basidia mostly ellipsoid to oval, sometimes subglobose or fusiform, 12-22(-30) × (7-)10-12 μm [Q=(1.09-)1.13-2.0(-2.71-3.16)], septate oblique, 2-spored, without or with very short sterigmata; 2-6(-8) basidia in chains, mostly 1-3 basidia with cytoplasm, the others on top collapsed, mostly with necks between basidia on top; basidia on the surface frequently with apical protuberance; clamped. Spores fusiform, both sides tapered, (14-)16-19(-21) × 5-7 μm [Q=(2.15-)2.50-3.45(-3.64)], germination by repetition and budding; secondary spores subglobose, width broader then length, 7-8 × 7.5-9.0 μm [Q=0.82-0.94], thin-walled, hyaline, smooth. Conidia absent. Vesicles absent. Swollen cells absent. Hyphidia absent. Hyphae hyaline, smooth, 2-4(-6) μm ø, clamped, sometimes anastomoses in subhymenium. Haustoria not seen.
Specimens：
Taiwan, Yilan county, between Dongao and Nanao, leg. C.-J. Chen, CCJ 1289, on decayed wood of Lauraceae, always associated with Ascomycetes, especially Hypoxylon spp; Taiwan, Pingdong county, Kenting National Park, leg. C.-J. Chen, CCJ 1341 & CCJ 1342.
Habitat：
null
Distribution：
null
References：
Bandoni, RJ. 1995; Boedijn, KB. 1934; Chen, CJ. 1998; Chen, PC and Hou, HH. 1979; Lowy, B. 1977; Lowy, B. 1964.
Provided：
C. J. Chen
Note：
The description is adapted to the type described by Boedijn (1934), although the spore measurements are broader than type. The large basidiocarps of S. magnum can not be distinguished from those of the genus Tremella macroscopically, particularly T. foliacea sensu lato, but differs in respect of long chained basidia and fusiform spores. Sirobasidium magnum always associated with Ascomycetes, especially with Hypoxylon spp. This is not detected from T. foliacea.
So far as known, excepting S. magnun all other Sirobasidium species are small size. The basidia on the surface of basidiocarps are necked between the collapsed basidia. This character resembles to what is lined out in the type illustrations. The trace of inconspicuous sterigmata occasionally can be detected from collapsed basidia. Although the basidiocarps are associated with Hypoxylon sp., the haustoria are not observed (Bandoni, 1995). The parasitic phenomenon is not well studied, but like T. fuciformis group and T. indecorata group, their basidiomata are habitually associated with ascomata or stromata of ascomycetes, suggesting mycoparasitism.
Tremella mayorgae Lowy (Lowy, 1977) is postulated to belong to Sirobasidium, and related to S. intermediae. The deciduous sterigmata, what he claimed, are typically sirobasidial basidiospores. According to his illustration and hymenial photographs, the type material of T. mayorgae are assumably very young basidiocarps of Sirobasidium. Additionally, Tremella clavisterigma Lowy (Lowy 1964) seems to be also a species of Sirobasidium from the sterigmata of Lowy's measurement and illustration. It represents a typical Sirobasidium species.
Phylum：Basidiomycota >> Class： Basidiomycetes >> Order： Tremellales 
BCRC Number：