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Page number:476 
Remarks (internal):Serendipita evanescens is easily distinguished from S. vermifera and S. sigmaspora by its spore shape, but less clearly distinguished from the American Exidiopsis prolifera (Rogers) Ervin. Hauerslev (1976) examined the type of E. prolifera and went on to describe S. evanescens as new because of its lack of inflated sub-basidial cells or clamp connexions, its lack of conspicuous clamps on the hymenial hyphae, and its longer wider spores. E. prolifera is also said to produce basidia on hyphal branches rather than in clusters and to form a thin but visible fruit body. Hauerslev (in Litt.) has kindly re-examined Danish material of E. evanescens and confirmed the presence of spores identical in shape to those of the new Devon collections.
The odd phenomenon of branching sterigmata is not infrequent among the Tremellales, Auriculariales, and Tulasnellales, but is exceptionally common in Serendipita species. Hauerslev (1976) describes and illustrates such sterigmata as being 'furcate', but in the Devon Serendipita collections there is always a clearly defined primary sterigma with one or more secondary sterigmata arising along its length, particularly near the tip. These secondary sterigmata are constricted at the point of attachment and swollen just above. Most form tiny branchlets, but Fig. 10 shows a most remarkable development of secondary and tertiary sterigmata which effectively quadruple the total length of the sterigmata. This appears to be an alternative to the elongation of sterigmata often seen in Exidiopsis and other more conventional tremellaceous fungi.
 
Description type:Non-original description 
Description:Serendipita evanescens (Hauersl.) P. Roberts, comb. nov.
(Fig. 10)
Sebacina evanescens Hauersl., Friesia 11: 102 (1976).
Exidiopsis evanescens (Hauersl.) Woj., Mala Flora Grzybów 2: 108 (1981).
Basidiomes not macroscopically visible. Hyphae thin, trailing, clamped, similar to S. sigmaspora. Basidia 2-4 septate, globose to subglobose, ca 10.0-11.5 x 9.5-10.0 µm, similar to S. vermifera. Basal clamp-connexions not seen, but immature basidia occasionally bear a short basal projection. Sterigmata similar to S. vermifera, but capable of extending up to 91.0 µm by means of branching secondary and tertiary sterigmata. Spores elongated, normally depressed or weakly allantoid, often constricted, narrowing at each end, frequently replicating, 15.0-20.5 x 4.0-5.5 µm (P. Roberts 78); 15.0-24.0 x 3.5-5.0 µm (P. Roberts 145); 17.0-24.0 x 3.5-4.0 µm (P. Roberts 344); (13.0-)15.5-22.0 x (3.0-)3.5-4.0 µm (P. Roberts 348); 15.0-23.5 x 3.0-4.5 µm (P. Roberts 503).
Specimens examined: on decorticated Picea log with Tubulicrinis accedens, Believer Forest, Dartmoor, Devon (SX 6576), 6 Jan. 1990, P. Roberts 78, K; same location and substratum, with Tulasnella sp., 1 Dec. 1991, P. Roberts 344, K; same date and details, P. Roberts 348, K; same location and substratum, with Tubulicrinis accedens, 7 Dec. 1991, P. Roberts 354, K; on decorticated Pinus log with Botryobasidium subcoronatum, Bovey Great Plantation, Devon (SX 8275), 12 Jan. 1991, P. Roberts 145, K; same location, on fallen Salix branch with Subulicystidium longisporum (Pat.) Parm., 2 Feb. 1991, P. Roberts 285, K; on decorticated branch, probably Picea, with Endoperplexa dartmorica, Fernworthy Forest, Dartmoor, Devon (SX 6583), 8 Mar. 1992, P. Roberts 372, K; on Pinus log with Tubulicrinis accedens, Slapton Wood, Devon (SX 8245), 3 Nov. 1992, P. Roberts 503, K.
 
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