Monographs Details: Hexagonia pobeguinii Har.
Authority: Fidalgo, Oswaldo & Fidalgo, Maria E. 1968. Polyporaceae from Venezuela. I. Mem. New York Bot. Gard. 17 (2): 1--34.
Description:Species Description - MACROSCOPIC CHARACTERS: Fruiting body annual, solitary, usually attached to the substrate by a small pilear portion, sometimes also by a broad portion, always sessile; pileus dimidiate to subreniform, applanate, 4-16.5 X 3-11X (0.2-)0.3-2.5(-6) cm; corky to subligneus; pilear surface ferrugineousbrown, MP-14G8 to MP-14J10, generally darker near to the insertion point, MP-SA12 (Autumn) to MP-8A10 (Sepia), usually with concentric, grayish, sulcated zones, MP-15C4 (Pampas) to MP-16C5 (Rat), initially pubescent to villose and silky then becoming glabrescent and somewhat fibrillose; margin straight, thin to thick, sometimes lighter than the pilear surface, beige, MP-12C5 (Manila) to MP-11E5 (Raffia). Context corky-fibrose to woody, homogeneous to subhomogeneous, subshining in section, dark ferrugineous brown, MP-14I9 (Mummy), MP-13F11 to MP-15H11 (Brown Sugar), (1-)2-4 mm thick, separated from the pubescent pilear surface by a shining, black line. Hymenial surface ferrugineous-brown, MP-15E11 (New Bronze), MP-16A12 (Biskra) to MP-8C11 (Bark), poroid, with angular, hexagonal pores, very rarely with the central pores splitting to appear like teeth, showing much variation in diameter, (0.5-)1-4(-9) pores per cm, mostly having 1-3 pores per cm at the center and 3-5 (-6) pores per cm near the margin; tubes velutinate, dark ferrugineous-brown, MP-15C10 (Madrid), MP-15A11 (Coffee) to MP-15A10 (English Oak), (0.1-)0.3-1(-2.5) cm long; dissepiments rather thick, (300-) 400-1200 µ thick. MICROSCOPIC CHARACTERS: Pilear surface characterized by a fasciculated trichoderm, with very short hairs, unbranched, associated in narrow fascicles, up to 250p long, formed of thick-walled to subsolid hyphae, (4.5-) 5-6 µ diam, with dark brown walls; black, shining layer separating the trichoderm from the context except at the growing margin, 38-50 (-60) µ thick, formed by yellowish-brown to brown hyphae, mostly closely associated and with periclinal orientation, with age the hairs falhng off partially, the black layer appearing as a cutis. Small masses of short generative hyphae, observed in several collections loosely interwoven like a plectenchyma, disposed around the insertion of the fascicles of hairs, attached to the cutis. Context and dissepiments formed by a trimitic hyphal system. Generative hyphae hyaline, thin-walled, branched, septate, with clamps, inconspicuous in the mature fruiting body, 1-2 (-3) µ diam. Skeletal hyphae yellowish-brown to brown, thin-walled to thick-walled, always with a distinct lumen, unbranched, very long, (3-) 4.5-7.5 (-8) µ diam, ribbonlike to fibrous, frequently with very thin, curved, delicate simple septa. Binding hyphae hyaline to yellowish-brown, thick-walled to solid, much branched, not septate, 1.5-3.5(-4) µ diam. Context when viewed in section sometimes presenting a differentiation in a fibrous upper layer, with the hyphae running periclinally and a small, compact lower layer, with the hyphae closely interwoven and not showing a definite orientation, many sections observed not showing such distinct differentiation but with most of the hyphae of the context having a periclinal orientation, giving to the whole context a fibrose aspect; the upper layer of the context with mainly fibrous skeletal hyphae of large diameter, 5-8 µ and large lumen, the lower part of the context and the dissepiments with skeletal hyphae more narrow and much more thickened. Dissepiments formed by skeletal and binding hyphae closely interwoven, without definite orientation, mixed with a small number of collapsed generative hyphae. Hymenium: setae, cystidia and cystidioles not found; seta-like cystidioid hyphae observed, represented by the projection into the hymenium of brown, thickened to mostly subsolid skeletal hyphae, in general projected 10-20 p beyond the basidia and having (3-)4.5-7.5(-8) µ diam; the apical portion of cystidioid hyphae usually fusiform and sometimes encrusted; hyphal pegs abundant, yellowish-brown to brown, cylindrical, not conical, usually narrow at the median part and then forked or somewhat branched, (60-) 100-180 X 18-30 (-60) µ, formed by aggregated, seta-like skeletal hyphae shghtly interwoven with a few generative hyphae; basidia clavate, hyaline, tetrasterigmate, 17-22.5 x (5-)6-8 µ; basidiospores hyaline, smooth, nonamyloid, cylindrical, 12.5-15.5 X (4-)4.5-5.5 µ.
Distribution and Ecology - Habitat, Hosts and Economic Importance: Hexagona pobeguini is said to occur on dead wood and dying branches. It was reported by Hopkins (1950: 91) on living branches of Brachystegia spicaeformis Benth. in Southern Rhodesia, by Doidge (1950: 517) on dying branches of Brachystegia randii Baker in Southern Rhodesia and on Pterocarpus angolensis DC. in Union of South Africa, Natal and, recently, by Pinto-Lopes (1965: 121) on decaying branches of Berlinea sp. in Manica e Sofala district, Mozambique. One collection was quoted as found on an old tree of Tamarix sp. in Kombeni, Kenya (DAOM). Apparently the associated rot is unknown. Specimens examined. Africa. CAMEROON. Locality and collector not indicated (herb. Patouillard at FH). CONGO. Locality not indicated, Pobeguin (herb. Patouillard at FH 2706, isotype of H. pobeguini); "Belgian Congo," Vanderyst (Lloyd 55235 at BPI); "Belgian Congo," Luja (Lloyd 55234 at BPI); locality not indicated, Dybowski (herb. Patouillard at F H 2706), Baudon (herb. Patouillard at F H 2706, mixed with specimens of H. hirta). DAHOMEY. Locality not indicated. Chevalier (herb. Patouillard at F H 2706). KENYA. Mazeras Forest, Maitland, Jun 1921 (BPI; DAOM 53746) ; Mazeras Forest, near Mombasa, Maitland (herb. J. R. AVeir 19554 at BPI); Kombeni, Kilifi Creek, near Mombasa, Mrs. Irwin 512, Sep 18, 1962 (DAOM 95127). MOZAMBIQUE. Tete: Zumbo, Cruz, Apr 1913 (C. Torrend, Fungi Sel. Exs. 234 at BPI and at FH); Zambezi River, Cruz, 1910 (URM 7188). TANGANYIKA. Ukami, near Mrogoro, Stuhlmann 50, May 16, 1890 (herb. Bresadola at BPI, merotype of H. stuhlmanni); locality not indicated, Hammerstein (Lloyd 55236 at BPI). Geographical Distribution. Hexagona pobeguini seems to be restricted to African countries, so far having been collected near the Equator, between 16° lat. N to almost 30° lat. S. It has been reported as occurring in Angola, between Condo and Quisondo, Pungu Andongo by A. L. Smith (1898: 177) as H. welwitschii, and from Huilla by Doidge (1950: 517); Congo by Hariot (1892: 28), from "Belgian Congo" by Lloyd (1911: 500; 1912b: 14) and by Heim (1933: 144), from Mobeka, Lower Congo and Kwango by Beeli (1930: 249); from Kenya by Natrass (1961: 35); from Mozambique, Zumbo by Torrend (1905: 219; 1914: 59) as H. pobeguini and H. stuhlmanni and also by Pinto-Lopes (1965: 121) from Manica e Sofala district; from Nigeria, Meko and Ayetoro by AVakefield (1914: 259); from Sierra Leone by Deighton (1937: 46); Southern Rhodesia by Hopkins (1939: 7; 1940: 412; 1950: 10) and by Doidge (1950: 517) from Salisbury; Tanganyika, without locality by Lloyd (1914: 4) and from Ukami, near Mrogoro by Hennings (1893: 29; 1895: 58; 1898: 184) as H. stuhlmanni; from Union of South Africa, Natal and Transvaal by Doidge (1950: 517). Apparently, the species is here reported for the first time from Cameroon and Dahomey.
Figs. 33, 66-72.
Hexagona stuhlmanni P. Henn.. Bot. Jahrb. 17: 29. 1S93. Type from Ukami, Tanganyika.
Hexagona wehcitschii A. L. Smith, Jour. Bot. 36: 177. 1898. Type from woods between Condo and Quisondo, Angola, deposited at BM. teste Lloj'd (1910: 17).
Type. Holotype collected by Pobeguin, deposited at Paris (PC); isotype at herbarium of Patouillard at FH.
Type Locality. Congo.
Basionym. Hexagona pobeguini Hariot, 1892.
Illustrations. Hennings in Engler, Pflanzenf. 1 (1): fig. 98, A-B (as H. stuhlmanni); Patouillard, Essai Taxon. Hymenom fig. 54, a-b. 1900 (as H. pobeguini); Lloyd, IMycol. Writ. 3(Syn. Hexagona): fig. 295. 1910; Mycol. Writ. 3 (Mycol. Notes 37): fig. 387. 1911 (as H. pobeguini).
Discussion. Hexagona pobeguini differs from the species placed in sect Hexagona in having the pilear surface velutinate or pubescent to glabrescent with age, microscopically represented by a fasciculated trichoderm with narrow short and unbranched hairs and also by the nonconical hyphal pegs. The remarkable hard consistency of the fruiting body, corky to woody, the seta-like cystidioid hyphae and the nonconical hyphal pegs are the most distinctive features of this species. The cystidioid hyphae and the hyphal pegs have been illustrated already by Patouillard (1900: fig. 54, b) and were also noticed by Lloyd (1912b: 14) who indicated that they were not of the same nature as the setae of Hymenochaete.
Hexagona pobeguini, as in other species of the genus, has a considerable variation in pore size; sometimes in the same collection specimens with large pores and some with small ones were found. Torrend (1935: 114) found in a collection from Congo specimens with large pores, 5 mm broad and 8-9 mm long and he also mentioned some small-pored specimens with pores 1-2 mm broad and 2-3 mm long. I compared an isotype of H. pobeguini (deposited at FH) with a merotype of H. stuhlmanni (deposited at BPI) and found them conspecific as Lloyd (1910a: 18) had already indicated. The type of H. welwitschii, a name also indicated by Lloyd (1910a: 17) as belonging to the synonymy of H . pobeguini, was not available for examination; however the original description of A. L. Smith (1898: 177) suggests H. pobeguini.
As is usual in Hexagona, basidiospores were very rarely found in dry specimens of H. pobeguini; only one collection (Cameroon at FH) was found to be abundantly fertile and the measurements of the basidiospores given in m y description are based on it.
Two collections that approach very closely the general habit of H. pobeguini were found but they have some minute differences in structure; I do not know if they are constant or not. One of the collections is an isotype of Hexagona zambeziana, a name published by Torrend (1914: 59-60) from material collected in Mozambique, Zumbo, now at FH (C. Torrend Fungi Sel. Exs 235) The second collection was collected by R. Fries, Nov 1911, in Northern Rhodesia Kalamboit was deposited at UPS and tentatively labelled by Svdow as H. apiaria which it is not; part of this collection is found in herb. G. Bresadola at BPI labelled as H. speciosa, which it is not. Tliese two collections differ from H. pobeguini by having rather incotis])icuous cystidioid hyphae, rarelv overlapping the basidial layer, 2 5-3.5 µ diam, mstead of the seta-like cystidioid hyphae of H. pobeguini The isotype of H. zambeziana has skeletal hyphae mucli thinner 2-3 7(-4) µ diam and a thinncT cutis in tbe pilear sm-face, 20-30 µ thick. The Northern Rhodesian collection (UPS) has only a beginning of cutis, with the outer hyphae of the context running periclinally but not very differentiated from the other hyphae of the context; however skeletal hyphae, (2-)2.5-5(-5.5) µ diam, are present more similar to those found in H. pobeguini. While the type of H. zambeziana is sterile, the Northern Rhodesian collection (UPS) is abundantly fertile, with hyaline, cylindrical, smooth basidiospores, (12.5-) 13.5-15.5 (-17) X 5-6 (-8.8) µ, shghtly larger than those observed in the Cameroon collection of H. pobeguini. In view of these facts more collections are necessary for study in order to determine if H. zambeziana is distinct enough to be considered a good species in the same section as H. pobeguini or if it is merely a variation of H. pobeguini.