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5. The genus Ostreichnion Duby Mem. Soc. Phys. Hist. Nat. Geneve 16: 22. 1862
Ostreion Saccardo, 1883
The genus Ostreichnion Duby
by E.W.A. Boehm
Duby (1862) established the genus Ostreichnion Duby for O. europaeum Duby and O. americanum Duby, with an etymology from Ostrea, a genus of oysters. Saccardo (1883) considered the name Ostreichnion to be invalid and instituted Ostreion Duby instead, a situation later rectified by Barr (1975). In studying Duby’s specimen of O. europaeum, Rehm (1886) considered the species to be a pedicilate form of Hysterium pulicare Pers.:Fr., leaving only the type species, O. americanum, which was later consigned to the earlier name O. sassafras (Schw.) Barr (Barr 1975). O. sassafras occurs on both sides of the Atlantic, as well as in China, and has been recovered from Sassafras, Quercus, Liriodendron and Liquidambar (Barr 1975; Bisby 1932; Teng 1933). Some confusion has existed as to the nature of spore septation in O sassafras. Most authors regarded the ascospores as “multiseptate” and Saccardo (1883) classified Ostreichnion, as Ostreion, in the phaeophragmiae. When longitudinal septa were observed they were regarded as pseudosepta (Bisby 1932). This eventually led Zogg (1962) to include Ostreichnion, as Ostreion, under the genus Mytilinidion. However, Massee (1895) had earlier noted and illustrated large muriform ascospores for both American and British specimens. Barr (1975) thus maintained Ostreichnion as a separate genus in the Mytilinidiaceae because of the muriform nature of the large ascospores, usually borne four to an ascus. Barr (1975) also proposed two additional species in the genus Ostreichnion: Hysterium nova-caesariense Ellis was removed from synonymy with Hysterographium flexuosum (Zogg 1962) and accepted as O. nova-caesariense (Ellis) Barr, known only from the type locality in NJ on Pinus, and having similar, but smaller, muriform ascospores as O. sassafras (Barr 1975). The second species accepted into the genus was O. curtisii (Duby) Barr, derived from Glonium curtisii (Duby) Lohman, an unusual fungus from the Coastal Plain and the southeastern United States to Louisiana (Lohman 1937) and also reported from Brazil (Zogg 1962). Barr (1975) made the transfer from Glonium in the Hysteriaceae to Ostreichnion in the Mytilinidiaceae, based on the broadly conchate ascocarps with a brittle, thin-walled prosenchymatous peridium enclosing a centrum similar to that found in O. sassafras, that is containing trabeculae in a gel matrix. However, O. curtisii possesses highly unusual ascospores that bear little resemblance to the muriform ascospores found in the previous two species (Barr 1975; Lohman 1937). In O. curtisii, the ascospores are sub-medially one-septate, with greatly thickened walls at the apices. Under different stains, the spore cytoplasm is clearly subdivided into numerous compartments, giving the impression of potentially muriform ascospores. Lohman (1937) provided details as to the highly unusual spore germination process in this fungus, which involves a distended apical plug and numerous median germ tubes, differing from that found in other species of Glonium which send out apical germ tubes.
Barr (1990): “Ascomata superficial, scattered or gregarious, bases sometimes immersed in substrate, conchate, medium to large sized; surface black, dull or shining, longitudinally striate at times; apex cristate, opening by longitudinal slit; peridium carbonaceous, brittle, composed of small heavily pigmented cells. Asci basal, clavate or cylindric. Trabeculae in gel matrix. Ascospores yellowish becoming reddish brown to dark brown, ellipsoid or nearly cylindric, ends obtuse or acute, symmetric or nearly so, straight or inequilateral, one- to several septate, usually one to three longitudinal septa, but these sometimes lacking constricted at first-formed septum; wall smooth or irregularly roughened; guttulate; overlapping biseriate in the ascus. Anamorphs not known. On woody angiosperms & gymnosperms. Type species: Ostreichnion americanum Duby = Ostreichnion sassafras (Schweinitz) Barr. Notes: The species have been dispersed in other genera, but Barr (1975) justified uniting them under Ostreichnion. The ascospores may show distosepta when young, & the ascus a suggestion of refractive ring around the wide ocular chamber. Such features are suggestive of the Massariaceae, but the shape of the ascomata & structure of the peridium dictate membership in the Mytilinidiaceae.”
Dichotomous Key to species of Ostreichnion Duby
[from Barr (1975 & 1990) for North American species]
1. Ascospores mostly one septate, ends thickened, (45-) 62 – 80 x (10-) 12 – 15 μm:
= Ostreichnion curtisii (Duby) Barr
2. Ascospores with both transverse & longitudinal septa.
a. Ascospores measuring 35 – 45 (-50) x 11 – 13 μm, with seven to thirteen septa:
= Ostreichnion nova-caesariense (Ellis) Barr
b. Ascospores measuring (65-) 76 – 100 (-135) x 20 – 32 μm with up to twenty seven septa:
= Ostreichnion sassafras (Schweinitz) Barr
Detailed Dichotomous Key to species of Ostreichnion Duby
[from Barr (1975 & 1990) for North American species]
1. Ascospores mostly one septate, ends thickened, (45-) 62 – 80 x (10-) 12 – 15 μm:
= Ostreichnion curtisii (Duby) Barr
Hysterium curtisii Duby, 1862
Gloniella curtisii (Duby) Saccardo, 1883
Hysterographium curtisii (Duby) Earle, 1901
Glonium curtisii (Duby) Lohman, 1937
Hysterium cyrillae Berkeley & Curtis, 1875
Glonium cyrillae (Berkeley & Curtis) Saccardo, 1883
Psiloglonium cyrillae (Berkeley & Curtis) Muller, 1962
Hysterium chlorinum Berkeley & Curtis, 1875
Glonium chlorinum (Berkeley & Curtis) Saccardo, 1883
Glonium macrosporium Tracy & Earle, 1896
Glonium gigasporum Ellis & Everhart in Herb. Ellis, ined.
Barr (1990): “ Ascomata 1mm long or longer, 440 – 470 μm wide, 330 – 385 μm high; surface longitudinally striate, shining, at times powdered with greenish coating; peridium 52 – 65 μm wide, blackened & encrusted externally, yellowish internally. Asci 150 – 180 (-220) x 25 – 30 (-40) μm. Ascospores (45-) 62 – 82 x (10-) 12 – 15 (-17) μm, yellowish brown, one septate, potentially seven- or more septate, longitudinal septum in one or more cells. Distribution on woody branches, southeastern USA; reported from Brazil (Zogg, 1962). Alabama: Tuskegee, Macon Co., Jan 1900, on Vitis rotundifolia, G.W. Carver, F. Col. 1536 as Hysterographium viticolum (MASS); Florida: Green Cove Springs, Clay Co., Winter 1884, collected from Sabal, G.W. Martin, Ellis N.A.F., 1321 as Hysterium lineolatum (MASS). Louisiana: Delta Regional Primate Center, 5 June 1976, M.E. Barr 6324b (MASS). South Carolina: Quercus, H.W. Ravenel, F. Car. 48 as Hysterium flexuosum (MASS). Note: Lohman (1937) described & illustrated details of the species which is quite common in southeastern USA. His account & illustrations of ascospore germination are illuminating.”
2. Ascospores with both transverse & longitudinal septa.
a. Ascospores measuring 35 – 45 (-50) x 11 – 13 μm, with seven to thirteen septa:
= Ostreichnion nova-caesariense (Ellis) Barr
Hysterium nova-caesariense Ellis, 1877
Mytilidion nova-caesariense (Ellis) Rehm, 1883
Hysterographium nova-caesariense (Ellis) Roumeguere, 1892
Barr (1990): “Ascomata up to 1mm long, 275 μm wide & high; surface faintly longitudinally striate; peridium 20 – 25 μm wide, blackish brown, brittle. Asci 100 – 130 x 30 – 40 μm. Ascospores 35 – 45 (-50) x 11 – 13 μm, dull brown, seven to thirteen septate, with one to three longitudinal septa. Distribution on periderm of Pinus rigida, known only from the type locality: USA New Jersey, Newfield, Gloucester Co., Apr. 1893, J.B. Ellis. Note: Zogg (1962) included this taxon as a synonym of Hysterographium flexuosum (Schweinitz) Saccardo, but the brittle peridium & trabeculae are quite different from the thick peridium & cellular pseudoparaphyses in Hysterographium as are the ascospore shapes.”
b. Ascospores measuring (65-) 76 – 100 (-135) x 20 – 32 μm with up to twenty seven septa:
= Ostreichnion sassafras (Schweinitz) Barr
Lophium sassafras Schweinitz, 1832
Mytilinidion sassafras (Schweinitz) Zogg
Ostreichnion americanum Duby, 1862
Ostreion americanum (Duby) Saccardo, 1883
Barr (1990): “Ascomata 1 – 1.5mm wide & high or up to 2mm high, about 750 μm wide in side view; peridium 26 – 40 μm wide at sides, 52 – 65 μm wide above, 104 – 115 μm wide at base. Asci 220 – 330 x 30 – 40 μm, usually only four spored. Ascospores (65-) 76 – 100 (-135) x 20 – 32 μm, yellowish to dark brown, end cells pallid, up to twenty seven septate with one to five longitudinal septa. Distribution on periderm or decorticated wood, southeastern USA; reported from China (Zogg, 1962 following Ten, 1933). Florida: Ocala, Marion Co., 1897 – 1898, R. Thaxter, Rel., Farlowianae 626 (NY). Georgia: Chattooga River, Rabun Co., 10 Mar 1934, Quercus, M.L. Lohman 583 (NY). North Carolina: South Toe River, Yancy Co., 30 Nov 1933, Quercus, M.L. Lohman 530; Old Fort, 22 May 1934, Liriodendron tulipifera, M.L. Lohman 579; Yadkinville, 12 Apr 1935, Quercus, M.L. Lohman 582 (all NY); South Carolina: Laurus, H.W. Ravenel (NY two collections); N. of Pickens, Pickens Col, 26 May 1934, Quercus, M.L. Lohman 580, 581 (all NY) – all listed as Ostreichnion americanum. Note: Zogg (1962) was unable to examine material & utilized earlier descriptions & opinions when he transferred the species to Mytilinidion. The ascospores of Ostreichnion sassafras are both notably larger & differently septate than in any species of Mytilinidion.”
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