Arcyria margino-undulata Nann.-Brem. and Y. Yamam., Proc. Kon. Ned. Akad. Wetensch., C 86: 218. 1983.
Description：
Fructifications sporangiate, scattered to sparsely gregarious, stipitate, 0.46-1.0 mm in total height. Sporangia globose, pale grayish white to pale ochraceous, 0.16-0.37mm in diameter, erect or nodding on a long stalk. Stalk long, tapering upward, brown to ochraceous below, paler and turning to pale grayish white to silky above, 0.32-0.73 mm long (ca 2/3-3/4 of the total height), filled with spore-like cells. Hypothallus membranous, transparent or brownish, discoid. Peridium early fugacious except for the basal calyculus. Calyculus undulate along the margins, plicate from the top of stalk, continuous to the undulate margins, 0.04-0.1 mm in diameter at the widest part. Capillitium firmly attached to the calyculus, consisting of colorless and transparent threads, 2.0-3.0 μm in diameter, prominently spinulate, with about 1 μm long spinules. Spores in mass concolorous with the sporangium, pale, nearly transparent and colorless by transmitted light, globose, 6.0-8.2 (-9.0) μm in diameter, nearly smooth by the margins, with prominent warts of small and large size scattering on the surface. Plasmodium not observed.
Specimens：
Taipei City: Shih-lin, Yangmingshan National Park, 26 Sept 1982, CHL B262b; 18 Sept 2001 (moist-chamber culture: 8/26-9/18/2001), CHL B2293; 23 Sept 2001 (moist-chamber culture: 8/26-9/23/2001), CHL B2294; 23 Sept 2001 (moist-chamber culture: 8/26-9/23/2001), CHL B2295; 22 Sept. 2001 (moist-chamber culture: 9/3-9/22/2001), CHL B2296. Taipei County: Shih-ting, Wenshan Botanical Garden of the National Taiwan Univ., 7 April 2000 (moist- chamber culture: 3/14-4/7/2000), Yang 99-12B3L3. Taichung County : Huisun Forest Station, 20 Dec 1997, CHL B1359 (Collected by P.H. Wang).
Habitat：
On leaf litter, fallen leaves of Miscanthus floridulus and Pseudosasa japonica, bark of living trees (Cryptomeria japonica).
Distribution：
Asia (Japan and Taiwan), North America (West Virginia, USA).
References：
Nannanga-Bremekamp, NE and Yamamoto, Y. 1983; Liu, CH, et al. 2002a.
Provided：
C. H. Liu
Note：
There are slightly differences between our specimen and the type specimen of Arcyria margino-undulata. First, the stalk of the type specimen is dark brown but ours is whitish. Second, the ratio of stalk to total height of fruiting bodies is ca 3/4 ~ 4/5 for the type specimen, and ours is 2/3 ~ 3/4. Nevertheless, based on the characteristics of the wrinkled margin of calyculus, the smaller size of fruiting bodies with long stalks, and the always globose sporangia, this specimen should belong to A. margino-undulata.
A. marginoundulata is very similar to the small fruiting bodies of A. cinerea (Bull.) Pers. In A. cinerea, the margine of calyclus is smooth, not wrinkled, and its capillitial threads are not decorated with long spines, and it is usually found on woody habibats. A. globosa Schwein. and A. afroalpina Rammeloo are also close to A. margino-undulata. A. globosa also has concentrical wrinkled margin of calyculus, but its calyculus is as deep as a cup-like structure and usually with a small ratio of stalk to the total height. A. afroalpina has distinct spinulose spores, but not nearly as smooth (cf. Nannenga-Bremekamp & Yamamoto, 1983).
Phylum：Myxomycota >> Class： Myxomycetes >> Order： Trichiales 
BCRC Number：