taxonID	type	description	language	source
8630123AFF9BD950FF2EFCB1FB38FAA1.taxon	description	Syntypus, box B. M. 4068 [BM 001085196]: This sample has been obtained from a culture from spores of the type, and it is better preserved than the lectotype. It consists of numerous sporocarps and the morphological and microscopic characters of this species are more uniformly developed compared to the lectotype specimen.	en	Moreno, G., Castillo, A., Thüs, H. (2022): Critical revision of Trichiales (Myxomycetes) at the Natural History Museum London (BM). Phytotaxa 567 (1): 1-20, DOI: 10.11646/phytotaxa.567.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.567.1.1
8630123AFF9BD950FF2EFAF1FD65F899.taxon	description	Box B. M. 3013 [BM 001247517]: The microscopic characters of capillitium and spore ornamentation observed under SEM are similar to those in the isolectotype.	en	Moreno, G., Castillo, A., Thüs, H. (2022): Critical revision of Trichiales (Myxomycetes) at the Natural History Museum London (BM). Phytotaxa 567 (1): 1-20, DOI: 10.11646/phytotaxa.567.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.567.1.1
8630123AFF9BD953FF2EF8E9FBD8FEEB.taxon	materials_examined	Syntype box B. M. 1483 [BM 001088829]: the sample consists of seven pieces of bark in which isolated sporocarps are found and most are broken. Sporocarps sessile or with a short stalk, 1 – 1.5 mm high, sporotheca spherical to clavate, 0.3 – 0.7 mm diam., yellow-ochreous in colour. Stalk shorter than diameter of the sporotheca. Peridium thin and membranous, with small papillae on the inside, dehiscence irregular. Capillitium formed by slightly branched yellowish filaments of 4 – 5 µm diam., free ends absent. Filaments with 2 – 3 tight spiral bands covered in small and abundant spines (very evident in phase contrast). The spirals are connected by longitudinal striae. Under the SEM the spiral bands show abundant obtuse apex spines or scattered teeth in the spirals; the abundant longitudinal striae are confirmed. Hypothallus dark discoid. Spores are globose to subglobose, 7.8 ‒ 9.9 (‒ 10) × (8 ‒) 8.2 ‒ 10 µm, av. 9.1 × 8.8 µm, Qav = 1.04 (n = 25), pale to pale yellowish in LM, warty, with marked and tight warts. Under the SEM, the ornamentation is of verrucate type, the verrucae are abundant and of irregular distribution.	en	Moreno, G., Castillo, A., Thüs, H. (2022): Critical revision of Trichiales (Myxomycetes) at the Natural History Museum London (BM). Phytotaxa 567 (1): 1-20, DOI: 10.11646/phytotaxa.567.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.567.1.1
8630123AFF9ED955FF2EFA04FDE8F95B.taxon	materials_examined	Samples B. M. 1489 [BM 001247518] and B. M. 2008 [BM 001247519]: the material conserved in BM is very scarce and no preparations have been made for the light microscope. We collected a small portion of the capillitium and spores and analyzed them under the SEM only. The capillitium is branched and with few free ends, filaments are 3 – 5 µm diam., with 3 – 5 tight smooth spirals bands, and irregular swellings, the latter being globose to oval up to 10 µm diam., with the same ornamentation or sometimes less marked than in the elaters. Spores are globose to subglobose, 10 – 14 µm diam., yellowish in mass. Under the SEM, the ornamentation is of baculate type, with abundant bacula of different sizes and irregular distribution.	en	Moreno, G., Castillo, A., Thüs, H. (2022): Critical revision of Trichiales (Myxomycetes) at the Natural History Museum London (BM). Phytotaxa 567 (1): 1-20, DOI: 10.11646/phytotaxa.567.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.567.1.1
8630123AFF9ED954FF2EF8ACFD89FE32.taxon	description	Box BM 2979 [BM 001247520]: this sample contains little material. Its characteristics in L. M. are very similar to BM 2978, except for the free ends of the filaments of the capillitium, which are frequently subglobose or rounded, similar to plate 172 by Lister (1925). The capillitium is scarcely branched, 3 – 4 µm in diam. Under the SEM acute to blunt ends of the capillitium become visible. Spores are globose to subglobose, 7.9 ‒ 11.7 (‒ 12) × 8.3 ‒ 11.9 µm, av. 9.8 × 10.1 µm, Qav = 1.03 (n = 20), slightly yellowish with warts in L. M. Under the SEM however, the spore ornamentation is confirmed to be similar to the type.	en	Moreno, G., Castillo, A., Thüs, H. (2022): Critical revision of Trichiales (Myxomycetes) at the Natural History Museum London (BM). Phytotaxa 567 (1): 1-20, DOI: 10.11646/phytotaxa.567.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.567.1.1
8630123AFF9DD956FF2EFF38FF6DFEEB.taxon	materials_examined	Type box B. M. 3004 [BM 001247521]: the material conserved in BM is very scarce, so we have taken only some spores to be able to observe the spore ornamentation under the SEM, and we have not been able to observe the capillitium. Spores are globose 11 – 12 µm diam., the spore ornamentation is formed by bacula of regular distribution under the SEM.	en	Moreno, G., Castillo, A., Thüs, H. (2022): Critical revision of Trichiales (Myxomycetes) at the Natural History Museum London (BM). Phytotaxa 567 (1): 1-20, DOI: 10.11646/phytotaxa.567.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.567.1.1
8630123AFF9DD956FF2EFA74FADEF864.taxon	materials_examined	Box B. M. 3174 [BM 001247522]: sporocarps sessile, globose, brown in color. Peridium thin, translucent, iridescent and light yellow. Capillitium abundant, yellowish-brown, with branched filaments of 4 – 7 µm diam., ornamented with 2 – 3 prominent smooth spirals bands, and 3 – 6 free ends with characteristic filiform extensions (penicillate), sometimes twisted or slightly spirally of 20 – 50 µm in length. Under the SEM the capillitium shows the smooth, tight spirals and characteristic filiform free ends. Spores are brownish in mass, globose, (12 ‒) 9.5 ‒ 11.9 (‒ 12) × (12 ‒) 9.5 ‒ 11.9 (‒ 12) µm, av. 10.7 × 10.7 µm, Qav = 1 (n = 25), yellowish by transmitted light, warty to spiny. Under the SEM, the spore ornamentation is of baculate type, formed by baculae of irregular distribution that sometimes join to form short ridges.	en	Moreno, G., Castillo, A., Thüs, H. (2022): Critical revision of Trichiales (Myxomycetes) at the Natural History Museum London (BM). Phytotaxa 567 (1): 1-20, DOI: 10.11646/phytotaxa.567.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.567.1.1
8630123AFF9DD956FF2EFA74FADEF864.taxon	description	Box B. M. 1542 [BM 001247523]: very abundant material, with sessile grouped sporocarps. Sporotheca globose, brownish. The macro- and microscopic characters are similar to sample B. M. 3174, but the elaters of the capillitium are somewhat wider (5 – 8 µm diam.) and the pointed penicillate free ends are more twisted. Spores pale yellowish in LM, globose, 9.7 ‒ 13.2 (‒ 14) × 9.7 ‒ 13.2 (‒ 14) µm, av. 11.4 × 11.4 µm, Qav = 1 (n = 25), spiny to warty. Under SEM, the spore ornamentation is similar to the one in sample B. M. 3174, except for the smaller and less dense baculae.	en	Moreno, G., Castillo, A., Thüs, H. (2022): Critical revision of Trichiales (Myxomycetes) at the Natural History Museum London (BM). Phytotaxa 567 (1): 1-20, DOI: 10.11646/phytotaxa.567.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.567.1.1
8630123AFF93D958FF2EFA3BFAB4F8A7.taxon	materials_examined	Box B. M. 4147 [BM 001247524]: the sample contains subglobose to globose sporocarps of 0.3 – 0.5 mm in diam., most of them broken and revealing the abundant bright yellow capillitium. Peridium single, thin and membranous, brittle, persistent at the base and with irregular dehiscence. Capillitium formed by yellow elastic tubular elaters, 5 – 6 µm diam., and with short pointed free ends of 5 – 10 µm in length. The elaters are ornamented with 3 – 4 spiral bands interconnected by transverse striations and showing spines that are difficult to discern in L. M. Under SEM the spines are distinctive with a height up to 0.5 µm. Spores are globose, 10.5 ‒ 13.8 (‒ 14) × 10.5 ‒ 13.8 (‒ 14) µm, av. 12.2 × 12.2 µm, Qav = 1 (n = 25), yellow in transmitted light, ornamented with a broad, irregular and sometimes fragmented reticulum. Under SEM the ornamentation is of cristate reticulate type with 3 – 4 meshes to a hemisphere and faint reticulation inside. The broad bands are up to 1 µm in height, which themselves are formed by a reticulum with numerous little holes.	en	Moreno, G., Castillo, A., Thüs, H. (2022): Critical revision of Trichiales (Myxomycetes) at the Natural History Museum London (BM). Phytotaxa 567 (1): 1-20, DOI: 10.11646/phytotaxa.567.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.567.1.1
8630123AFF90D95BFF2EFA0CFD9CF963.taxon	materials_examined	Box B. M. 2907 [BM 001247525] (type): the material on two pieces of bark is scarce. From the few sporocarps (sessile or with short stalk) a small sample of capillitium and spores was taken for study by LM and SEM. The capillitium is formed by yellowish elaters 4 – 5 µm in diam. Under SEM elaters show 3 – 4 smooth and not very tight spiral bands, with pointed free ends (up to 20 µm in length). Sometimes before the apex a globose broadening is visible. Spores are globose, (10 ‒) 10.1 ‒ 13.6 × (10 ‒) 10.1 ‒ 13.6 µm, av. 11.8 × 11.8 µm, Qav = 1 (n = 25), yellowish in transmitted light and densely warted. Under SEM the spore ornamentation is of the pilate type and tight. Sometimes interconnected at the top of pila forming small reticulae.	en	Moreno, G., Castillo, A., Thüs, H. (2022): Critical revision of Trichiales (Myxomycetes) at the Natural History Museum London (BM). Phytotaxa 567 (1): 1-20, DOI: 10.11646/phytotaxa.567.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.567.1.1
8630123AFF91D95AFF2EFB06FAB2FAF6.taxon	materials_examined	Type box B. M. 2942 [BM 001089762]: only a small sample of the capillitium and spores was taken for study under the SEM. The capillitium shows elaters 3 – 5 µm in diam. with smooth and tight spirals bands (3 – 4), with pointed free ends up to 40 µm in length. Spores are globose to subglobose and 9 – 12 µm in diam. Under SEM the spore ornamentation is of pilate type, the capita of adjacent pila are sometimes connected by fine threads and form short ridges.	en	Moreno, G., Castillo, A., Thüs, H. (2022): Critical revision of Trichiales (Myxomycetes) at the Natural History Museum London (BM). Phytotaxa 567 (1): 1-20, DOI: 10.11646/phytotaxa.567.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.567.1.1
8630123AFF91D95AFF2EFA3AFBCBF95E.taxon	materials_examined	Box without historic collection number, barcode [BM 001089762]: leg. anon., Hertf. VC 20 [= Hertfortshire, Vicecounty 20]: only a small sample of capillitium and spores was taken for study by LM and SEM. The capillitium is orange in mass, yellowish-brown by LM. Elaters 4 – 5 µm in diam., with 3 – 4 regular spiral bands interconnected by transverse striations and showing spines that are difficult to observe in LM, but distinctive under the SEM. Elaters with very short pointed free ends up to 5 µm in length. Spores are globose, 8.8 ‒ 10.6 × 8.6 ‒ 10.6 µm, av. 9.7 × 9.7 µm, Qav = 1 (n = 25), yellowish in transmitted light and reticulated. Under the SEM the ornamentation is of the simple reticulate type, the reticulum is made up of 8 – 10 meshes of different sizes per semicircle, with low muri.	en	Moreno, G., Castillo, A., Thüs, H. (2022): Critical revision of Trichiales (Myxomycetes) at the Natural History Museum London (BM). Phytotaxa 567 (1): 1-20, DOI: 10.11646/phytotaxa.567.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.567.1.1
8630123AFF97D95FFF2EFA71FD6DFECE.taxon	materials_examined	Lectotype: — JAPAN. Tokyo Prefecture: Tokyo, gardens of the Akasaka Imperial Palace, 35 º 40 ’ 48 ” N 139 º 43 ’ 43 ” E, on Prunus grayana Maxim., 23 Jan 1928, The Emperor of Japan [Emperor Shôwa, Hirohito] and presented by him to the British Museum, B. M. 4067, [box: BM 001085195, slide: BM 001223775] (BM!), as Hemitrichia imperialis G. Lister. Syntype: — JAPAN. Tokyo Prefecture: Tokyo, gardens of the Akasaka Imperial Palace, 35 º 40 ’ 48 ” N 139 º 43 ’ 43 ” E, a culture from spores of the typus [see B. M. 4067] obtained by Dr. H. Hattori in the Biological Laboratory, Imperial Palace, Tokyo, 30 Apr 1928, B. M. 4068, [box: BM 001085196, slide:, BM 001223776] (BM!), as Hemitrichia imperialis G. Lister.	en	Moreno, G., Castillo, A., Thüs, H. (2022): Critical revision of Trichiales (Myxomycetes) at the Natural History Museum London (BM). Phytotaxa 567 (1): 1-20, DOI: 10.11646/phytotaxa.567.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.567.1.1
8630123AFF97D95FFF2EFA71FD6DFECE.taxon	description	This species is mainly characterized by a capillitium formed by filaments with 2 – 3 spirals ornamented with spines on their edges and by its small spores of approx 7 µm in diam. The description is based on the lectotypus specimen, which is in a rather bad condition and we analyzed a small portion of the sporotheca of the lectotype and of the syntype material. The two samples were also studied by Rammeloo (1984). The culture sample B. M. 4068 is in perfect condition and maintains the complete sporocarps and is better preserved than the lectotypus, an assessment already published by Rammeloo (1984) who also pointed out that the ornamentation of the capillitium was somewhat more strongly pronounced in the field collection. However, we found very similar ornamentation of the capillitium in both collections (Figs 1 b, f). Nannenga-Bremekamp (1982) considered Hemitrichia imperialis as a species within the genus Arcyria, but she did not make a valid recombination for this genus and proposed the name as a synonym of Arcyria stipata (Schwein.) Lister. We do not agree with this conclusion because this A. stipata develops filaments of the capillitium with interconnected spiral bands from which spines emerge (Nannenga-Bremekamp 1991). This morphology clearly differs from what we have observed in the type material of H. imperialis.	en	Moreno, G., Castillo, A., Thüs, H. (2022): Critical revision of Trichiales (Myxomycetes) at the Natural History Museum London (BM). Phytotaxa 567 (1): 1-20, DOI: 10.11646/phytotaxa.567.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.567.1.1
8630123AFF94D95FFF2EFED3FA8EFC0F.taxon	materials_examined	Additional material examined: — UNITED KINGDOM. England: Beaminster, Dorset, on leaves, 2 Feb. 1898, leg. G. Lister, B. M. 3013, (BM!). This species is characterized by its sessile, yellowish sporocarps and by its large reticulated spores of 14.7 ‒ 18.5 µm in diam., ornamented with large-meshed reticulum (6 – 9 meshes to a hemisphere) and rather broad muri. These characteristics coincide with those studied in both samples by Rammeloo (1984). The sample B. M. 3013 is not indicated by Lado & Wrigley de Basanta (2018). We had only a small portion available for SEM and the microscopic characters of capillitium and spore ornamentation observed are similar to those in the isolectotypus.	en	Moreno, G., Castillo, A., Thüs, H. (2022): Critical revision of Trichiales (Myxomycetes) at the Natural History Museum London (BM). Phytotaxa 567 (1): 1-20, DOI: 10.11646/phytotaxa.567.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.567.1.1
8630123AFF94D95FFF2EFC13FCE0FB77.taxon	description	This species is characterized by its sessile or short-stalk sporocarps, small spores 7.8 ‒ 9.9 (‒ 10) × (8 ‒) 8.2 ‒ 10 µm in diam., and capillitium filaments ornamented with spiral bands with abundant spines. Our observations confirm the data assembled by Rammeloo (1984) based on the same collection.	en	Moreno, G., Castillo, A., Thüs, H. (2022): Critical revision of Trichiales (Myxomycetes) at the Natural History Museum London (BM). Phytotaxa 567 (1): 1-20, DOI: 10.11646/phytotaxa.567.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.567.1.1
8630123AFF94D95EFF2EFABBFAF9FE86.taxon	materials_examined	Material studied: — UNITED KINGDOM. England: West Midlands, Dudley Castle, January 1891, leg A. Camm, ex Herb. Lister coll. Myzetozoa, B. M. 1489, [BM 001247518 = box] (BM). England: West Midlands, Dudley Castle, February 1890 and January 1891, leg A. Camm, ex Herb. H. W. Howard, B. M. 2008, [BM 001247518 = box] (BM).	en	Moreno, G., Castillo, A., Thüs, H. (2022): Critical revision of Trichiales (Myxomycetes) at the Natural History Museum London (BM). Phytotaxa 567 (1): 1-20, DOI: 10.11646/phytotaxa.567.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.567.1.1
8630123AFF94D95EFF2EFABBFAF9FE86.taxon	discussion	This species is mainly characterized by its branched capillitium with few free ends and filaments with characteristic irregular swellings of globose to oval shape. After studying the type material from Sri Lanka Lister (1894) concluded that is an independent species within the genus Hemitrichia Rostaf., due to its tangled and branching capillitium of threads with irregular expansions. On the other hand, this species was combined by Ing (1965) as Trichia contorta var. karstenii, since he did not observe important differential characters with respect to T. contorta, apart from a capillitium with branched elaters and a tendency to form plasmodiocarps. The name Hemitrichia karstenii was accepted by Martin & Alexopoulos (1969), Mitchell (1980) and Flateau (1990). However, it has been cited as Trichia contorta var. karstenii by Lado & Pando (1997), Nannenga-Bremekamp (1991) and Neubert et al. (1993). To differentiate both taxa, we have analyzed the material of BM under SEM. We observed spiral bands in the capillitium distributed more irregularly in Trichia contorta (Ditmar) Rostaf. and the spore ornamentation is very different between both taxa. Spores of Hemitrichia karstenii have ornamentations of the baculate type, but in Trichia contorta they are of the pilate type. This ornamentation type in T. contorta has also been indicated by Rammeloo (1974) and Neubert et al. (1993) for European material, and by Wang & Li (2006) for Chinese specimens. These sporal differences are sufficient to treat them as autonomous species. Due to the current lack of a full revision for this species group, except for preliminary data on Austral representatives by Ronikier et al. 2020 to confirm its phylogenetic placement, and for the reasons previously stated, we follow Lister and keep it for the time being in the genus Hemitrichia.	en	Moreno, G., Castillo, A., Thüs, H. (2022): Critical revision of Trichiales (Myxomycetes) at the Natural History Museum London (BM). Phytotaxa 567 (1): 1-20, DOI: 10.11646/phytotaxa.567.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.567.1.1
8630123AFF95D95EFF2EFE8BFE30FCC7.taxon	description	Additional material studied: — UNITED KINGDOM. England: Dorset, Westover Hill, Charmouth, on heathland, 29 Mars 1907, K. Furse, B. M. 2979, (BM). This follicolous species is mainly characterized by its capillitium with branched filaments ornamented with faint and smooth spirals and blunt free ends with a short appex. The sample B. M. 2978 has been proposed as lectotypus (Lado & Wrigley de Basanta, 2018), however, the authors did not have access to the sample B. M. 2979, which we have also studied here. This species was proposed as a variety of Hemitrichia intorta (Lister) Lister by Lister (1894). This status was also suggested by Martin & Alexopoulos (1969). Our observations agree with the results of an SEM study of the lectotype material carried out by Rammeloo (1984), which leaves no doubt to separate this species from H. intorta, since H. leiotricha presents smooth and not spiny capillitium, and the spore ornamentation is different, as well as the inner surface of the peridium.	en	Moreno, G., Castillo, A., Thüs, H. (2022): Critical revision of Trichiales (Myxomycetes) at the Natural History Museum London (BM). Phytotaxa 567 (1): 1-20, DOI: 10.11646/phytotaxa.567.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.567.1.1
8630123AFF95D95EFF2EFCCBFCA1FA22.taxon	materials_examined	Type (as Hemitrichia karstenii): — [CZECK REPUBLIK]. Bohemia: Klatovy, Chudenice, in cortice Carpinus betulus, 6 August 1887, leg Celakovsky fil., B. M. 3004, [BM 001247521 = box] (BM!). We have studied the type of Perichaena cornuvioides L. F. Celak. As the material is very scanty, we analyzed only a small portion and we were only able to study the spore ornamentation under SEM. This ornamentation seems similar to that of the Hemitrichia karstenii samples studied, although the latter shows less homogeneous ornamentation. We were unable to prepare the capillitium for LM and SEM, so we cannot confirm its morphology. Lister (1911), indicates that “ the type of P. cornuvioides appears to be an abnormal form of H. karstenii, in which the capillitium shows no trace of spirals, and is marked with many small bladder-like or cup-shaped expansions ” and maintains the possibility that it could be a Perichaena corticalis (Batsch) Rostaf. based on the form of the fruiting body. In an earlier study (Moreno et al. 2000) we have observed a spore ornamentation very similar to P. corticalis formed by baculae. However, if we abide by the original description by Čelakovský (1893) in figure 6 of Plate 1, a capillitium without spirals was observed, more typical of Perichaena, so the proposed synonymity with Hemitrichia karstenii or with Trichia contorta appears doubtful to us.	en	Moreno, G., Castillo, A., Thüs, H. (2022): Critical revision of Trichiales (Myxomycetes) at the Natural History Museum London (BM). Phytotaxa 567 (1): 1-20, DOI: 10.11646/phytotaxa.567.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.567.1.1
8630123AFF95D941FF2EFA77FA94FDC2.taxon	materials_examined	Material studied: — UNITED KINGDOM. England: Bedfordshire, Luton, 15 April 1908, Miss K. Higgins, B. M. 3174, (BM), as Prototrichia metallica. UNITED KINGDOM. England: Lyme Regis, Charton, 1890 - 1894, A. Lister, B. M. 1542, [box: BM 001247523] (BM), as Prototrichia flagellifera.	en	Moreno, G., Castillo, A., Thüs, H. (2022): Critical revision of Trichiales (Myxomycetes) at the Natural History Museum London (BM). Phytotaxa 567 (1): 1-20, DOI: 10.11646/phytotaxa.567.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.567.1.1
8630123AFF95D941FF2EFA77FA94FDC2.taxon	discussion	This species is characterized by sessile sporocarps (rarely short-stalked), a branched filamentous capillitium with smooth spiral bands and free ends with 3 – 6 characteristic filiform (penicillate) extremities attached to the upper part of the sporotheca. According to Rammeloo (1983), this species is variable in most of its characters, as reflected in the rather high number of synonyms, but he did not study any of the two samples at BM described here. Prototrichia schroeteri Meyl. was described as a nivicolous species with fruiting bodies appearing during spring in areas with long lasting snow cover (Meylan 1921). Morphologically it was further separated from P. metallica by its always stipitate brown sporocarps, by its dense, persistent capillitium, attached to the apex of the stipe that maintains the morphology of the sporocarp once the peridium is lost, by the disconnection of the inner surface of the peridium; and by the colour of the spores. The morphological differences appear to be mostly ambiguous characters which do not allow a safe separation of the two taxa. If the unusual fruiting time of P. schroeteri was the result of exceptional weather conditions in the collection year or if it really represents a constant character can only be judged based on new and sequenced collections. The constant presence of a stalk could have been another unambiguous character as all sporocarps from the samples of Prototrichia metallica studied here were sessile. The microscopic characteristics are very similar in both species. However, Kowalski (1975) indicated that he had collected stipitated samples of P. metallica and he concluded that the two names are synonymous, a taxonomic treatment with which we agree, until the separation is re-examined by molecular studies. The microscopic characters of sample B. M. 1542 assigned to Prototrichia flagellifera are similar to those of sample BM 3174 of P. metallica, so we conclude that the BM-sample is a mislabelled collection of P. metallica. Although we have not studied type material of P. flagellifera, we consider both species synonymous (Lado 2005 – 2022).	en	Moreno, G., Castillo, A., Thüs, H. (2022): Critical revision of Trichiales (Myxomycetes) at the Natural History Museum London (BM). Phytotaxa 567 (1): 1-20, DOI: 10.11646/phytotaxa.567.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.567.1.1
8630123AFF8AD941FF2EFDD7FDBFFA93.taxon	materials_examined	Material studied: — URUGUAY. Tacuarembo: September 1928, Dr. G. Herter, B. M. 4147, [BM 001247524 = box] (BM). This species is characterized by sessile yellowish sporocarps. The capillitium is composed of narrow (5 – 6 µm diam.) elaters. Under SEM we can see that it is surrounded by spiral bands with transverse striations and small spines, scarcely visible by LM. Free ends are pointed. Spore ornamentation has a net of variable morphology. The reticulum consists of wide discontinuous bands which form a broken mesh. The bands also are composed of a reticulum with smaller meshes. Martin & Alexopoulos (1969) and Farr (1958, 1976) considered Trichia affinis as a synonymous species of T. favoginea (Batsh) Pers. and T. persimilis Karsten., since “ none of the differences supposed to separate this species is constant ”. Although this group presents very similar characters, we follow the taxonomic treatment given by NannengaBremekamp (1991) and Lado (2005 – 2021), who consider them to be different species. According to our experience, the diameter of the capillitium is a good character to separate Trichia favoginea (8 – 10 µm diam.) from T. affinis and T. persimilis (4 – 6 µm diam.). Without this additional diagnostic character the separation of these latter two species can be difficult. For T. affinis, the presence of a capillitium with smooth or with small spines, spiral bands and spores with a broken reticulum is characteristic, while for T. persimilis, the presence of a capillitium with spiny spiral bands, and spores with a reticulum in the form of islets or patches of reticulum are typical. Also T. affinis differs from T. favoginea in that the latter does not have globose sporocarps, they are cylindrical and the spores are larger (13 – 15 µm diam.).	en	Moreno, G., Castillo, A., Thüs, H. (2022): Critical revision of Trichiales (Myxomycetes) at the Natural History Museum London (BM). Phytotaxa 567 (1): 1-20, DOI: 10.11646/phytotaxa.567.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.567.1.1
8630123AFF8AD940FF2EFAE7FB91FE87.taxon	materials_examined	Type (of Trichia intermedia): — CZECH REPUBLIC. Bohemia prope Chudenice, 18 July 1884, L. Čelakovský, B. M. 2907, [box: BM 001247525] (BM!).	en	Moreno, G., Castillo, A., Thüs, H. (2022): Critical revision of Trichiales (Myxomycetes) at the Natural History Museum London (BM). Phytotaxa 567 (1): 1-20, DOI: 10.11646/phytotaxa.567.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.567.1.1
8630123AFF8AD940FF2EFAE7FB91FE87.taxon	discussion	Trichia contorta is characterized by its sessile and globose yellowish-brown sporocarps, with delicate peridium, elaters of capillitium with free ends pointed, and spores 11 – 13 μm in diameter, weakly ornamented with spines, which appear as pili under SEM. This typical ornamentation has repeatedly been observed previously e. g. by Rammeloo (1974), Neubert et al. (1993) and Wang & Li (2006). The macro- and microscopic characteristics of the type of T. intermedia studied in this paper coincide with those indicated for T. contorta by the previous authors, so we consider both species synonymous. Trichia contorta was described by Ditmar (1813) as Lycogala contortum, who provided an excellent plate showing the fructifications and the capilicon formed by short elaters. The name Trichia contorta (Ditmar) Rostafinski may be invalid as it is a yonger homonym to T. contorta G. H. Otth. (1869: 62). Based on the rather vaguely worded protologue and in the absence of access to type material, we follow Lado (2005 - 2022) in considering T. contorta G. H. Otth. a doubtful name and in the interest of nomenclatorial stability continue the use of the long established name T. contorta (Ditmar) Rostafinski. This species has been confused with Hemitrichia karstenii, from which it is clearly differentiated by its capillitium, formed by elaters with abundant free ends and spores that present an ornamentation formed by pili under SEM (Rammeloo 1974), where interconnected pili can be seen, sometimes forming small reticula.	en	Moreno, G., Castillo, A., Thüs, H. (2022): Critical revision of Trichiales (Myxomycetes) at the Natural History Museum London (BM). Phytotaxa 567 (1): 1-20, DOI: 10.11646/phytotaxa.567.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.567.1.1
8630123AFF8AD940FF2EFAE7FB91FE87.taxon	diagnosis	Two similar species to Trichia contorta with sessile sporocarps are T. varia (Pers. ex JF Gmel.) Pers., which differs by its capillitium with spiral bands of irregular distribution, and T. alpina Meyl., with a darker peridium, almost black, wider capillitium (5 – 10 μm in diam.), and larger spores (16 – 18 μm in diam.).	en	Moreno, G., Castillo, A., Thüs, H. (2022): Critical revision of Trichiales (Myxomycetes) at the Natural History Museum London (BM). Phytotaxa 567 (1): 1-20, DOI: 10.11646/phytotaxa.567.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.567.1.1
8630123AFF8BD940FF2EFE82FA95FD49.taxon	materials_examined	Syntype: — UNITED KINGDOM. England: Essex, Epping Forest, Drift Way, 51.66 ºN 0.05 ºE, on hornbeam leaves, 29 Nov 1896, A. G. Phear, B. M. 2942, [BM 001089762 = box, BM 001089171 = slide] (BM!), as Trichia botrytis var. munda.	en	Moreno, G., Castillo, A., Thüs, H. (2022): Critical revision of Trichiales (Myxomycetes) at the Natural History Museum London (BM). Phytotaxa 567 (1): 1-20, DOI: 10.11646/phytotaxa.567.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.567.1.1
8630123AFF8BD940FF2EFE82FA95FD49.taxon	discussion	Trichia munda is a rare and little quoted species, which was considered as a variety of Trichia botrytis (J. F. Gmel.) Pers. by some authors such as Lister (1897). Meylan (1927) considered it as a separate species from T. botrytis. Among other reasons he pointed out that T. munda fructifies from a white plasmodium and not purple-brown as T. botrytis. We agree with the separation of both taxa. Trichia munda shows fructifications isolated and with smaller sporocarps (1 – 1.5 mm in total height), a minute sporotheca, slender stalk (2 – 2.5 times the diam. of the sporotheca) and strongly ornamented spores. The spore ornamentation under SEM presents very differentiated “ pila ” in which the head is densely mamiliferous, very similar to the spore ornamentation of Metatrichia floripara (Rammeloo 1981).	en	Moreno, G., Castillo, A., Thüs, H. (2022): Critical revision of Trichiales (Myxomycetes) at the Natural History Museum London (BM). Phytotaxa 567 (1): 1-20, DOI: 10.11646/phytotaxa.567.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.567.1.1
8630123AFF8BD940FF2EFD5EFE5DFBB2.taxon	materials_examined	Material studied: — UNITED KINGDOM. Hertfortshire: Vicecounty 20, leg. anon., s. n., [BM 001247525 = box], as Trichia scabra Rostaf. This species is characterized by its crowded and sessile sporocarps, elaters with spiral bands with small spines interconnected by longitudinal striations and spores reticulated. Results of an SEM study carried out by Hatano (1986 plate 23 and 24) of this species with material from Japan, are supported with the observation made on the material from BM, regarding the characteristics of both spore ornamentation and the elaters of the capillitium.	en	Moreno, G., Castillo, A., Thüs, H. (2022): Critical revision of Trichiales (Myxomycetes) at the Natural History Museum London (BM). Phytotaxa 567 (1): 1-20, DOI: 10.11646/phytotaxa.567.1.1, URL: http://dx.doi.org/10.11646/phytotaxa.567.1.1
