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 Physarum citrinum
BiostatusPresent in region - Indigenous. Non endemic
Article: Stephenson, S.L. (2003). Myxomycetes of New Zealand. Fungi of New Zealand. Ngā Harore o Aotearoa 3: xiv + 238 p. Hong Kong: Fungal Diversity Press.
Description: Fruiting body a stalked sporangium, scattered to closely gregarious, 0.8–2.0 mm tall. Sporotheca globose to subglobose or reniform, somewhat flattened to invaginated below, 0.5–0.8 mm in diameter. Stalk stout, calcareous, sulcate, tapering upward, sometimes expanded at the base, yellow to yellow orange or dull orange, opaque, very short to slightly more than one half the total height of the fruiting body. Hypothallus membranous, discoid to contiguous for a group of sporangia, often shiny, colourless to yellow or brown. Peridium consisting of a single layer, thin, membranous, nearly completely covered with yellow calcareous squamules and patches, bright yellow or ochraceous to pale yellow or yellowish grey, sometimes limeless and iridescent at the base. Columella small, more or less conic or convex, yellow, sometimes absent or replaced by a pseudocolumella. Capillitium dense, delicate, consisting of relatively small, mostly rounded or polygonal (but with a few elongated or branching), yellow lime nodes connected by rigid, hyaline filaments with flat expansions at many of the junctions. Spores dark brown in mass, light violaceous brown by transmitted light, nearly smooth to unevenly warted, sometimes with scattered, more prominent, single or grouped warts, 8–10 µm in diameter. Plasmodium yellow.
Habitat: Decaying wood, usually with bryophytes also present.
Distribution: Considered to be cosmopolitan by Martin & Alexopoulos (1969) but probably more characteristic of temperate regions of the world, albeit never common. Farr (1976) reported the species from South America, Hagelstein (1944) from North America, and Ing (1999) from Europe. First reported from New Zealand by Lister & Lister (1905), based on a specimen collected in Taranaki.
Notes: This rather distinctive species is very similar in appearance to Physarum globuliferum but can be distinguished on the basis of its usually larger overall size and the brighter yellow colour of both the peridium and stalk. Ing (1999) reported that P. citrinum is now much less common in the British Isles than was the case during the early part of the 20th century. The reasons for this apparent decline are unknown.
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