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 Add this item to the list   Phellinus populicola Niemelä, n. sp.
Page number:94 
Remarks (internal):On living individuals of Populus species (sect. Populus), in Europe mainly on P. tremula, often in necrotic depressions. Young stage resembles Phellinus igniarius var. igniarius externally, but differs in the smaller and narrower spores, thinner skeletal hyphae, lighter trama and transitional context, and in the host and cultural characters.
Some authors have already drawn attention to this taxon. Illustrations are given by Borisov (1940), Doma?ski (1954), Jahn (1962) and Roll-Hansen (1967), and the second and last authors also studied its culture. The taxon was regarded as a form of P. igniarius by Erikson & Strid (1969) and Done (1974: 243). Eriksson and Strid described the morphological characteristics of young fruit bodies: the smooth, slightly cracked, greyish upper side and thick brown margin; Donk mentioned the rimose black crust characteristic of older fruit bodies. In these two publications the taxon was called P. igniarius f. tremulae E. Komar. (Komarova 1964).
Unfortunately, I was unable to obtain the original material of P. igniarius f. tremulae E. Komar. When publishing the form, (Komarova (1961: 220) mentioned only its growth on aspen, giving no description. A few words under the description of P. tremulae suggest that her form is the taxon discussed here.
Externally, young and medium-aged P. populicola resembles the type variety of P. igniarius in having smooth, broad zones and a rounded margin. The characters distinguishing P. populicola are thinner skeletal hyphae in the dissepiments (up to 4 µm in P. populicola vs. up to 5-6 µm in P. igniarius), its lighter colour in section, the thin context in large specimens and Populus tremula as host. The spores of P. populicola are somewhat smaller and distinctly more ellipsoid than those of P. igniarius and P. nigricans, coming rather close to those of P. lundellii. Very old fruit bodies are characterized by a deeply rimose, black crust in the older parts. In the final stage this species has the largest fruit bodies in the P. igniarius complex, at least in NW Europe.
Morphologically, it differs from the other varieties of P. igniarius, although some specimens (e.g., some collections from Ulmus and Corylus were found to be confusingly similar. In such cases it could be differentiated by microscopy and culturing. So at present the only recorded hosts are Populus tremula and P. alba. It presumably occurs only in the sect. Populus, since finds from Populus balsamifera belong to P. igniarius.
P. populicola can always be separated from P. tremulae by checking whether the dissepi-ments hyphae are parallel (P. tremulae) or interwoven.
Phellinus vaninii Lyub., described on Populus tremula from the eastern part of the Soviet Union (Lyubarskij1962: 115), differs from P. populicola in, for instance, the smaller pores,
slightly smaller spores and longer setae. Phellinus Pilátii Cerny (Cerny 1968: 2), described on Populus alba and P. x canescens from Czechoslovakia, differs from it in the smaller spores, presence of setal hyphae. effused growth and cultural characters (Cerny 1968, and my own results).
P. populicola grows on fairly large, living trees, but stays alive for some years after the tree has died. Fruit bodies seldom develop around dead branches as in P. tremulae (Niemelä 1971). Instead, they appear on wounds or intact bark, and cause the death of adjacent bark and cambium (unlike those of P. tremulae), thus forming a large necrotic area, which gradually turns into a depression around the fruit body as the rest of the trunk becomes thicker. Apart from heartwood, it also decays sapwood, whereas P. tremulae is typically a heartrot species.
It has some economic importance as a parasite on aspen, but much less than P. tremulae. My observations in Czechoslovakia and Poland suggest that in central Europe it partially replaces P. tremulae as a parasite on aspen.
Description type:Original description 
Description:Phellinus populicola Niemelä, n. sp.
? P. igniarius (L. ex Fr.) Quél. f. tremulae E. Komarova, Opredelitel' trutovyh gribov Belorussii: 220. 1961 (nom. inval.: no Latin description, no proper Russian description, not typified; original material not obtained).
Not Fomes igniarius (L. ex Fr.) Fr. f. tremulae Bondarcev, Trudy po Lesnomu Opytnomu Delu v Rossii 37: 20. 1912 [= P. tremulae (Bond.) Bond. & Borisov].
Fruit body perennial, single or growing in twos or threes, woody-hard, attached to substrate narrowly, or broadly when growing in depression (Figs. 8-11).
When young semi-spherical, 3.5-5 cm in diameter. When mature obtuse or applanate, 5-15 cm wide, 3.5-5 (-13) cm thick at base, projecting 5-9 (-12) cm from substrate. Old fruit bodies growing remarkably large, 25-30 cm wide, 15-20 cm thick, ungulate.
Crust at first not very dark, light greyish brown, Burnt umber, Smoke brown, with smooth broad zones, often with faint lustre, fissures few and mostly along furrows; in old specimens almost black and densely criss-crossed by deep fissures, finally rimose, and often covered by moss. Fully developed crust 0.2-0.7 mm thick, in section black and glassy-hard.
Sterile margin 0.5-2 cm wide, rounded, olive-Gold brown to Cinnamon brown.
Hymenial surface even, slightly oblique in young specimens, horizontal in ungulate fruit bodies, with no tendency to effused growth, Leather brown to Cinnamon brown, sometimes darker, Burnt umber. Pores regular, 4-6 (-7) per mm, round or slightly ellipsoid, 0.10-0.14 mm in inner diameter, dissepiments ca. 0.05-0.10 mm, thicker in irregular parts. Dissepiment edges matt, rounded.
Context of young fruit body 1-2 cm thick, 1/3 to 2/3 of total thickness; in large specimens around 1 cm thick, very thin in relation to tubelength (Fig. 9), light Sepia to Burnt umber. Transitional layer bordering tubes softer, Leather brown, especially at base marmorate with radial cream stripes. Tube layer (trama) Leather brown, old tubes filled with cream mycelium. Core mostly absent, sometimes rudimentary, dark brown, next to wood.
Spores (4.8-)5.1-5.7 (-6.0) x (3.8-)4.0-4.8(- 5.0) µm, single, broadly ellipsoid, obtuse-based, with somewhat applanated supra-apicular region. Wall of medium thickness, 0.4-0.6 µm, smooth, colourless. Apiculus ca. 0.5 x 0.5 µm. Spores hyaline, nonamyloid, indextrinoid, acyanophilous. Deposited spores some-what larger (within given limits) and with smaller variation. (Fig. 1).
Basidia clavate, 8-12 x 5.5-8 µm, with four sterigmata 2.5-3.5 µm long. Basidioles similar in shape, 8-9 x 4.5-4.s µm. Both organs collapsing after sporulation, leaving loose honey-comb structure with cells 4-5 µm in diam., walls 0.5-1 µm thick and 4-5 µm high. Hymenial setae (12.2-) 15.0-20.5 (-23.0) x (5.0-)6.2-7.8(-9.5) µm, index (2.0-) 2.3-2.6(-2.0). Setae mostly rather few, seldom numerous, yellowish brown, rather thick-walled, subulate but often with very sharp apex, rather often malformed.
Subhymeniuns indistinct.
Hyphal system dimitic. Hyphae nonamyloid,. indextrinoid, acyanophilous, skeletals darkening in KOH.
Hyphae in hymenial trama interwoven. Generative hyphae 2.2-3.0 µm, thin-walled, hyaline, branched, simple-septate. Skeletal hyphae (2.5-) 3.0-4.0 (-4.5) µm in diameter, unbranched, rarely simple-septate, walls 1.1-1.8 µm thick, yellowish brown in Melzer's reagent.
Context hyphae similar to those of trama but radially subparallel, skeletals up to 5-6 µm thick and with wider lumina. In lower part of transitional layer of context patches of colourless inflated generative hyphae.
Core setae 25-150 µm long, 7-12 µm thick, with reddish brown walls 2-5 µm thick, straight or lumpy with blunt or pointed tips. Between them areas of skeletal and generative hyphae.
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