Karstenia 17: 77-86. 1977 On Fennoscandian polypores 5. Phellinus pomaceus TUOMO NIEMELA NIEMELA, T. 1977: On Fennoscandian polypores 5. Phellinus pomaceus. - Kars­ tenia 17: 77-86. The anatomy, distribution, pathology and cultural characters of Phellinus pomaceus (Pers. ex S.F. Gray) Maire are described on the basis of ca. 470 North European specimens. The main anatomical features separating the species from the P. igniarius complex are the subparallel dissepimental hyphae and thin-walled skeletals in the context. P. pomaceus is fairly common in hemiboreal and temperate southern Fennoscandia, but does not extend farther north. In this region, it occurs almost exclusively on Prunus species, mainly P. domestica L., P. cerasus L. and P. spinosa L., but it has been reported only twice from P. padus L., the commonest Prunus species in Fennoscandia. The cultural characters and anatomy show that P. pomaceus is taxonomically homogeneous in N Europe, except perhaps for a form growing on Crataegus. A lectotype is selected for P. pomaceus, and the taxonomic position of some closely related taxa (Polyporus corni Velen ., Fames pomaceus f. crataegi Baxter, Fomitiporia prunicola Murr.) is shortly discussed. Tuomo Niemela, Department of Botany, University of Helsinki, Unioninkatu 44, SF-00170 Helsinki 17, Finland Phellinus pomaceus (Pers. ex S.F. Gray) Maire is Material was received from the following herbaria: BG, C, GB, H, HFR, HPP, KUO, L, LE, MICH, NFRI (Nor­ closely related to the P. igniarius complex (Niemela wegian Forest Research Institute, As), NPPI (Norwegian 1972, 1974, 1975), being especially similar in its Plant Protection Institute, As), 0, OULU, PRC, PRM, S, morphology. However, in the microscope and in TRH, TUR and UPS . In addition, collections were studied culture it is clearly separated from the species of from the private herbaria of Dr. John Eriksson (Goteborg, Sweden), Dr. Ingvar Nordin (Goteborg), Dr. Ake Strict that group, and its specific status is at present (Stockholm) and myself. almost universally acknowledged . This applies to the The cultural strains are maintained in the author's typical pileate specimens growing on pi urn, cherry, collection in H, and the corresponding herbarium speci­ and other species of the genus Prunus s. lat. mens are deposited in Hand HFR. The picture is not, however, so simple everywhere. In Central and South Europe, closely related taxa Phellinus pomaceus occurring on hosts other than Prunus need a Phellinus pomaceus (Pers. ex S.F. Gray) Maire, Mus. detailed comparison with the basic material, and in Barcin. Sci. Nat. Op. I5 (Fungi Catal.): 37 . 1933 . Type: no North America, certain effused species of Phellinus original designation, lectotype: 'Polyporus pomaceus. show a very close affinity to P. pomaceus. In this Boletus. Gallia. Hb. Pers. Ad truncos praesertim Pruno­ paper a detailed description is given of the North rum et Cerasorum.' (Herb. Persoon, L, no. 910.263-397, selected here). European P. pomaceus. [Boletus pomaceus Persoon, Observ. Mycol. 2: 5. 1799.]- Boletus pomaceus Pers. ex S.F. Gray, Nat. Materials and methods Arrangem. British Plants I: 642. 1821 . -Fames pomaceus (Pers. ex S.F. Gray) Lloyd, Mycol. Writ. 2: 8. 1908. - The description is based on ca. 470 Fennoscandian speci­ Ochroporus pomaceus (Pers. ex S.F . Gray) Donk, Mede­ mens. The procedures followed in measuring the structural deelingen Bot. Mus. Herb. Rijksuniversiteit Utrecht 9: 250, details, and collecting the other data were the same as in 1933 . my previous studies on the genus. The microscopical For synonyms, see Niemela (1975: 120) and Ryvarden & measurements were made in Melzer's reagent. Calonge (1976). 78 T. Niemelti Figs. 1-3. Phellinus pomaceus. - 1: Imbricate fruit bodies on the vertical trunk of Pnmus cerasus, x 0.5 (specimen Aalto 537, H).- 2: Solitary fruit bodies on P. domestica, x 0.7 (Niemela 446, H).- 3: Culture, grown on malt agar, at 24°C, for two weeks. Petri dish diameter 9 em (Akerman 236, HFR). Photo Tuomo Niemela. Perennial, single, or often in groups and Edge roundish, or often somewhat acute, sterile confluent (Figs . 1-2). Fruit body flat and widely margin (best seen in effused part) 1-3 mm wide, attached to substrate, pileate or more often thickly cinnamon. effused-reflexed, young specimens seldom thinly Hymenial surface even, oblique, concave in pro­ resupinate, more often nodular. Pileate part project­ file, golden brown - greyish brown - light grey, ing 1-4.5 em from substrate, 1-4 em thick at base according to state of growth, with slight glitter when and 2.5-7 em wide, old specimens sometimes growing actively, such parts turning rust brown if larger. Mature effused or effused-reflexed specimens bruised when fresh. Pores regular, (4-) 5-6 (-7) grown on under sides of branches ellipsoid when per mm, round or ellipsoid, sometimes elongated or viewed from below, 3-15 x 2-6 em, 8-20 mm angular if tightly packed, 0.11-0.18 (-0 .29) x thick. 0.09-0.16 mm in inner diameter (measured from Surface various shades of light grey, with tint of transverse section), most pores 0.10-0.18 mm in sepia or ochre towards margin, cinnamon when diameter, dissepiments 0.02-0.10 mm thick. growing actively, lustreless, minutely rough, growth Dissepiment edges matt in weathered specimens, zones wide, flat and irregular, or indistinct. Old velvety when growing actively, rounded. specimens with dark grey, irregularly rimose upper Context in section relatively thick at base, 3-16 surface. Surface glabrous and compact, but with no (-25) mm thick, yellowish brown, lustrous espe­ distinct crust, except in oldest rimose fruit lbodies. cially if split when dry; subiculum in effused speci- Karstenia 17. 1977 79 O<J 4 0 .~. Fig. 4. Anatomical details of Phe/linus pomaceus: a) spores, b) generative hyphae from dissepiment, c) skeletal hypha from dissepiment, d) hymenial setae, e) skeletal hyphae from context, f) dissepiment edge in vertical section (specimen 21.IV .1973 Tuomikoski, H). mens mostly very thin, 1 mm or less . Oldest context comb structure with cells 4-5.5 1-1m in diam., and near substrate lighter brown because of white radial with walls 0.8-1.6 1-1m thick and 4-5 1-1m high. stripes, no core (in few cases very rudimentary core Hymenial setae (12 .0-) 15 .5-19.5 (-29.0) x present). Tube layer (trama) in section light brown, (5 .5-) 6.3-7.4 (-8.5) 1-1m, length/ width index in older specimens with fairly distinct annual layers 2.2-2.6 (-2.9) . Setae sometimes few but always 3- 5 mm thick, mycelium filling old tubes white. present, reddish to yellowish brown, thick-walled, Fresh fruit body easily cut; dried specimens subulate, regular with stout apex and sometimes woody, lighter than e.g. those of P. igniarius and with heel. more easily split with a knife. Subhymenium indistinct. Hypha! system dimitic. Hyphae nonamyloid, indextrinoid, non-cyanophi­ Spores (5.0-) 5.8-6.4 (-7.0) x (4 .0-) lous (except hypha! tips), skeletals darkening in 4.6-5.0 (-5.4) 1-1m, single or loosely agglutinated KOH. in very fertile specimens, ellipsoid, with somewhat Hyphae in hymenial trama subparallel. Genera­ applanated supra-apicular region (Fig. 4) . Wall thin, tive hyphae 2- 3 1-1m, with 0.2-0.4 1-1m thick 0.3-0.5 1-1m, smooth, hyaline, nonamyloid, index­ hyaline walls, branched and simple-septate. Skeletal trinoid, weakly cyanophilous. Apiculus small, 0.4 X hyphae 2.5-3.7 (-4.0) 1-1m in diam., unbranched, 0.4 1-1m. In dry material spores often collapsed and seldom simple-septate, with yellowish brown, angular. 0.9-1.5 1-1m thick walls, or with thinner yellow Basidia thickly clavate, 10-13 X 6-7.5 1-1m, walls in proximal parts. with four sterigmata 3 1-1m long; basidioles 9-12 X ·context hyphae with distinct radial orientation, 5.5-6.5 1-1m; collapsed hymenium visible as honey- though not strictly parallel. Generative hyphae up to 80 T. Niemela 3.5 1-1m thick, colourless, few . Skeletal hyphae in form does differ in certain respects, though some of context (3.0-) 4.0-6.1 1-1m in diam.; hypha! walls the differences, e.g. those in the spore measure­ 0.5-1.0 (-1.3) #Jill, i.e. thin in relation to lumina; ments, may not be important; the N American skeletals often collapsing and flattening, yellowish material of P. pomaceus also has somewhat smaller brown also when thin-walled, unbranched but often spores than the European one (Overholts 1953) . and distinctly septate. No decisions should be made about the identity of the form on Crataegus before more European In Fennoscandia a southern species, locally material is available. Baxter's results suggest that common in the hemiboreal and temperate parts (oak cultural studies might be especially useful in zone). On dying and dead standing trunks of Prunus deciding whether the Crataegus form is a separate species, mostly P. domestica and P. cerasus in taxon or not. orchards. Other unsolved problems are those posed by the resupinate Phellinus pomaceus var. prunastri (Pers. Taxonomy ex S.F. Gray) Pat., which should be compared with an American species, Fomitiporia prunicola Murr., P. pomaceus is genetically rather uniform in north­ and the South European P. pomaceus var. oleae ern Europe, as is evident from the simple host Hart. ex Erikss . These do not occur in North spectrum, and lack of marked variation in the Europe, and are not dealt with further there. The cultural characters. It can be separated from the taxonomy of this species group is much more species of the P. igniarius complex by its yellowish complicated in North America than in Europe, and brown, lustrous context, subparallel skeletal hyphae can hardly be solved without cultural studies.