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Fungal remains in the lycopod megaspore Triletes rugosus (Loose) schopf
Review of Palaeobotany and Palynology, 41 (1984): 199--204 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands
199
FUNGAL REMAINS IN THE LYCOPOD MEGASPORE TRILETES RUGOSUS (LOOSE) SCHOPF
SARA P. STUBBLEFIELD and THOMAS N. TAYLOR Department of Botany, The Ohio State University, Columbus, OH 43210 (U.S.A.) (Received October 25, 1983;revised version accepted February 1, 1984)
ABSTRACT Stubblefield, S.P. and Taylor, T.N., 1984. Fungal remains in the lycopod megaspore Triletes rugosus (Loose) Schopf. Rev. Palaeobot. Palynol., 41: 199--204. Spherical fungal bodies within the lycopod megaspore Triletes rugosus are described from permineralized plant remains of Pennsylvanian age. Specimens reach 70 um in diameter and occur singly or in groups. Although some specimens lie free within the megaspore and show no connection with either host tissue or other fungal tissue, others are embedded in a stroma-like material, and are attached to hyphal filaments. The fungal wall is smooth and unornamented and extensively layered. Specimens resemble fossil Glomuslike chlamydospores in size and shape, but differ in the organization of the wall. When compared with extant organisms they are most similar to the sporangia of zoosporic fungi. INTRODUCTION T o d a t e the C a r b o n i f e r o u s m y c o f l o r a has n o t b e e n e x h a u s t i v e l y d o c u m e n t e d . Past w o r k has f o c u s e d o n relatively large, c o n s p i c u o u s o r g a n i s m s such as t h e so-called "fossil s p o r o c a r p s " (e.g., S p o r o c a r p o n , D u b i o c a r p o n , M y c o c a r p o n , Traquairia) (Williamson, 1 8 8 0 ; M c L e a n , 1 9 2 2 ; B a x t e r , 1 9 6 0 ; Davis and L e i s m a n , 1 9 6 2 ; S t u b b l e f i e l d and T a y l o r , 1983), P a l a e o s c l e r o t i u m ( R o t h w e U , 1 9 7 2 ; D e n n i s , 1976), and P r o t o a s c o n ( B a t r a et al., 1964). Organisms such as t h e s e invite s t u d y b e c a u s e t h e y are large and well-preserved; t h e y are easily m a n i p u l a t e d and yield a b u n d a n t , r e a d i l y i n t e r p r e t a b l e detail. H o w e v e r , such m a t e r i a l c o n s t i t u t e s o n l y a small p o r t i o n o f the fungal rem a i n s p r e s e r v e d in the fossil r e c o r d . C o u n t l e s s o t h e r fungi have g o n e unrec o r d e d , p r o b a b l y b e c a u s e t h e y are difficult t o m a n i p u l a t e and y i e l d little in the w a y o f s t r u c t u r a l detail. I n d i r e c t e v i d e n c e o f fungal a c t i v i t y has g e n e r a l l y n o t b e e n recognized. As a result, t h e diversity o f C a r b o n i f e r o u s fungi has b e e n u n d e r e s t i m a t e d , and t h e l i t e r a t u r e c o n t a i n s little d a t a t o facilitate f u r t h e r s t u d y . T h e a p p l i c a t i o n o f e l e c t r o n m i c r o s c o p y to the s t u d y o f fossil fungi p r o v i d e s a p o w e r f u l t o o l t h a t p r o m i s e s t o e x p a n d o u r k n o w l e d g e o f t h e s e o r g a n i s m s greatly. T h e p r e s e n t p a p e r describes s o m e fungal r e m a i n s discovered within the megaspores of a heterosporous, Carboniferous lycopod.
0034-6667/84/$03.00
© 1984 Elsevier Science Publishers B.V.
200 MATERIALS AND METHODS Permineralized fungal remains are f o u n d within coal balls from the wellknown Lewis Creek locality in southeastern K e n t u c k y (G ood and Taylor, 1970). Specimens come f r o m the Breathitt F o r m a t i o n which is early--middle Pennsylvanian (= Westphalian A--B equivalent) in age (G ood and Taylor, 1970; Phillips, 1980). A p p r o x i m a t e l y 25 specimens o f the l y c o p o d megaspore Triletes rugosus (Loose) S c h o p f contain spherical fungal bodies. Material was prepared f or light m i c r o s c o p y using standard coal ball techniques. In preparation for scanning electron microscopy, small portions o f the coal ball were removed, etched with dilute hydr oc h l ori c acid, and dried in an Autosamdri Critical Poi nt Drier. T he dried material was m o u n t e d on standard stubs, coated with gold, and examined on a Hitachi S-500 Scanning Electron Microscope. In preparation f or transmission electron m i croscopy, blocks were then treated with 10% sodium cyanide for approxi m at el y t w o hours to remove the gold, and cellulose acetate peels were subsequently made from t h e etched surfaces. Appropriate portions o f these peels were coated with agar on a millipore filter under suction. T h e y were then treated with 5% uranyl acetate, d ehydr a t e d, and e m b e d d e d in Spurr's Low Viscosity Plastic following standard techniques. E m b e d d e d specimens were sectioned and examined at 75 kV. Specimens bear collection numbers 1 0 7 2 8 - - 1 0 7 6 5 in The Ohio State University Paleobotanical Collections. DESCRIPTION Spherical bodies up to 70 pm in diameter are found within the l y c o p o d megaspore Triletes rugosus (Loose) Schopf. Megaspores are contained within intact cones o f F l e m i n g i t e s ( L e p i d o s t r o b u s ) schopfii Brack (Brack, 1970; Brack-Hanes and Thomas, 1983). Although t hey are well preserved, those spores invaded by fungi do not exhibit a distinct, well-preserved megag a m e t o p h y t e . Fungal specimens oc c ur singly (Plate I, 1, 5; Plate II, 3) or in close association with o t h e r similar structures (Plate I, 2--4). Although m a n y of the fungal bodies are free within the megaspore (Plate I, 1, 5; Plate II, 3), o t h e r are e m b e d d e d in a c o m p a c t stroma-like tissue (Plate I, 2--4). The spherical structures are smooth-walled and exhibit no evidence of papillae or o t h e r p r e f o r m e d germination sites. Their walls seem t o be at least t w o layers thick PLATE I 1. Triletes rugosus in section view with isolated fungal body (arrow). 2124 F Bot. #4.
× 100. 2. Sporangia embedded in stroma-like matrix. 2124 F Bot. #4. × 340. 3. Triletes rugosus containing fungal remains. Note hyphae on inside surface of megaspore wall (arrow). 2124 F. × 80. 4. Higher magnification of 3. Note sporangial walls. 2124 F. × 500. 5. Individual sporangium and associated stromatie tissue. Note small hollow area at left (arrow). 2124 F. × 600.
t
-3
.-t
202
in transmitted light, and layering is even more prominent at the ultrastructural level where four or five units are seen (Plate II, 2). There is some variability in the number of layers, suggesting possible preservational modification including degradation and shrinkage. Individual wall layers are solid and homogenous at the ultrastructural level (Plate II, 2). The amount of tissue associated with the fungal bodies varies considerably. In some specimens it is nearly absent, while in others it occupies approximately 60% of the interior of the spore. In transmitted light and scanning electron microscopy the tissue is usually amorphous (Plate I, 2, 4, 5). There is no evidence of intact, parenchymatous cells typical of preserved megagametophytic tissue. However, occasional small, round openings are visible (Plate I, 5) which may represent either hyphae in section view or immature fruiting structures. In one instance a fungal body is attached at two points to a hyphal strand which is continuous with the more loosely organized stroma-like material (Plate II, 5). This material is probably fungal in origin, at least in part, although it may also include fragments of degraded megagametophytic tissue. Other hyphaelike filaments are sometimes present along the inner surface of the megaspore wall (Plate I, 3; Plate II, 1). These strands are restricted to this area, and apparently do not ramify throughout the interior of the megaspore. These vary in diameter and are n o t easily seen in reflected light because of the sectional nature of the preparations. There is no physical connection between these filaments and other structures within the megaspore. DISCUSSION Like many undescribed fungi present in Pennsylvanian spores, the organisms within Triletes rugosus are relatively small and indistinct bodies which represent only a portion of one phase of the life cycle. They are assumed to be fungal in origin on the basis of their morphological similarity to other Carboniferous fungi, particularly fossil Glomus-like chlamydospores {Wagner and Taylor, 1982). The physical connection of the spherical bodies with hyphae-like strands strengthens this interpretation. To our knowledge comparable specimens have not been described from the fossil record. Although the present material resembles the Glomus-like chlamydospores found throughout the Paleozoic, it m a y be distinguished from fossil Glomus-like specimens on the basis of wall structure. Despite superficial similarities in the organization of the wan visible in transmitted light, differences are apparent at the ultrastructural level. The walls in the present material exhibit more layers than is typical of the fossil Glomus. The affinities of these specimens are presently indeterminable due primarily to the lack o f contents in the spheres. However, among extant forms they show some similarity to sporangia of chytridiaceous fungi or perhaps to the chlamydospores of oomycetes. Members of these groups were well established by the Pennsylvanian (see Tiffney and Barghoorn, 1974) and chytrids are associated with lycopods t o d a y (Sorokin, 1872; Zopf, 1887).
203
PLATE II
1. Higher m a g n i f i c a t i o n o f fungal h y p h a e seen o n m e g a s p o r e wall in Plate I, 3. 2 1 2 4 F. x 650. 2. S e c t i o n t h r o u g h sporangial wall s h o w i n g m u l t i p l e layers. I n n e r m o s t surface o f wall indic a t e d b y arrow. Bar r e p r e s e n t s 4 urn. D i r e c t i o n of s e c t i o n is parallel t o t h e bar scale. 2 1 2 4 F. X 5000. 3. I n d i v i d u a l fungal s p o r a n g i u m . 2 1 8 4 F. x 2000. 4. Higher m a g n i f i c a t i o n o f s t r o m a - l i k e tissue. 2 1 8 4 F. x 2000. 5. S p o r a n g i u m a t t a c h e d t o h y p h a l strand. 2 1 2 4 F Bot. #4. x 350.
204 ACKNOWLEDGMENTS
The authors wish to thank Ms. Kathleen Pigg who drew our attention to these organisms and Drs. Roland L. Seymour and Lennart Holm for useful discussion concerning their structure and affinities. This research was supported in part by funds from the National Science Foundation (DEB8213060). REFERENCES Baxter, R.W., 1960. Sporocarpon and allied genera from the American Pennsylvanian. Phytomorphology, 10 : 19--25. Baxter, R.W., 1975. Fossil fungi from American Pennsylvanian coal balls. Univ. Kansas Paleontol. Contrib., 77: 1--6. Batra, L.R., Segal, R.H. and Baxter, R.W., 1964. A new Middle Pennsylvanian fossil fungus. Am. J. Bot., 51: 991--095. Brack, S.D., 1970. On a new structurally preserved arborescent lycopsid fructification from the Lower Pennsylvanian o f North America. Am. J. Bot., 57: 317--330. Brack-Hanes, S.D. and Thomas, B.A., 1983. A re-examination of Lepidostrobus Brongniart. Bot. J. Linn. Soc., 86: 125--133. Davis, B. and Leisman, G.A., 1962. Further observations on Sporocarpon and allied genera. Bull. Torrey Bot. Club., 89: 97--109. Dennis, R.L., 1976. Palaeosclerotium, a Pennsylvanian age fungus combining features of modern Ascomycetes and Basidiomycetes. Science, 192 : 6 6 - 6 8 . Good, C.W. and Taylor, T.N., 1970. On the structure of Cordaites felicis Benson from the Lower Pennsylvanian o f North America. Palaeontology, 13 : 29--39. McLean, R.C., 1922. On the fossil genus Sporocarpon. Ann. Bot., 3 6 : 7 1 - - 9 0 (PI.VIII--X). Phillips, T.L., 1980. Stratigraphic and geographic occurrences of permineralized coalswamp plants -- Upper Carboniferous of North America and Europe. In: D.L. Dilcher and T.N. Taylor (Editors), Biostratigraphy o f Fossil Plants -- Successional and Palaeoecological Analysis. Dowden, Hutchinson and Ross, Stroudsburg, PA, pp.25--92. Rothwell, G.W., 1972. Palaeosclerotium pusillum gen. et sp. nov. : A fossil eumycete from the Pennsylvanian o f Illinois. Can. J. Bot., 50: 2353--2356. Sorokin, N., 1872. Mycological investigations. Tr. O.-Va. Jest-Ispyt., 2: 1--46. Stubblefield, S.P. and Taylor, T.N., 1983. Studies of Carboniferous fungi I. The structure and organization of Traquairia (Ascomycota). Am. J. Bot., 70: 387--399. Tiffney, B.H. and Barghoorn, E.S., 1974. The fossil record of the fungi. Occas. Pap. Farlow Herb. Cryptogam. Bot. Harv., 7 : 1--42. Wagner, C.A. and Taylor, T.N., 1982. Fungal chlamydospores from the Pennsylvanian of North America. Rev. Palaeobot. Palynol., 37 : 317--328. Williamson, W.C., 1880. On the organization of the fossil plants of the Coal-measures -Part 10. Including an examination o f the supposed radiolarians of the Carboniferous rocks. Philos. Trans. R. Soc. Lond., 171 : 493--539. Zopf, W., 1887. Ueber einige niedere Algenpilze (Phycomyceten) und eine neue Methode ihre Keime aus den Wasser zu isolieren. Abh. Naturforsch. Ges. Halle, 17: 77--107.
199
FUNGAL REMAINS IN THE LYCOPOD MEGASPORE TRILETES RUGOSUS (LOOSE) SCHOPF
SARA P. STUBBLEFIELD and THOMAS N. TAYLOR Department of Botany, The Ohio State University, Columbus, OH 43210 (U.S.A.) (Received October 25, 1983;revised version accepted February 1, 1984)
ABSTRACT Stubblefield, S.P. and Taylor, T.N., 1984. Fungal remains in the lycopod megaspore Triletes rugosus (Loose) Schopf. Rev. Palaeobot. Palynol., 41: 199--204. Spherical fungal bodies within the lycopod megaspore Triletes rugosus are described from permineralized plant remains of Pennsylvanian age. Specimens reach 70 um in diameter and occur singly or in groups. Although some specimens lie free within the megaspore and show no connection with either host tissue or other fungal tissue, others are embedded in a stroma-like material, and are attached to hyphal filaments. The fungal wall is smooth and unornamented and extensively layered. Specimens resemble fossil Glomuslike chlamydospores in size and shape, but differ in the organization of the wall. When compared with extant organisms they are most similar to the sporangia of zoosporic fungi. INTRODUCTION T o d a t e the C a r b o n i f e r o u s m y c o f l o r a has n o t b e e n e x h a u s t i v e l y d o c u m e n t e d . Past w o r k has f o c u s e d o n relatively large, c o n s p i c u o u s o r g a n i s m s such as t h e so-called "fossil s p o r o c a r p s " (e.g., S p o r o c a r p o n , D u b i o c a r p o n , M y c o c a r p o n , Traquairia) (Williamson, 1 8 8 0 ; M c L e a n , 1 9 2 2 ; B a x t e r , 1 9 6 0 ; Davis and L e i s m a n , 1 9 6 2 ; S t u b b l e f i e l d and T a y l o r , 1983), P a l a e o s c l e r o t i u m ( R o t h w e U , 1 9 7 2 ; D e n n i s , 1976), and P r o t o a s c o n ( B a t r a et al., 1964). Organisms such as t h e s e invite s t u d y b e c a u s e t h e y are large and well-preserved; t h e y are easily m a n i p u l a t e d and yield a b u n d a n t , r e a d i l y i n t e r p r e t a b l e detail. H o w e v e r , such m a t e r i a l c o n s t i t u t e s o n l y a small p o r t i o n o f the fungal rem a i n s p r e s e r v e d in the fossil r e c o r d . C o u n t l e s s o t h e r fungi have g o n e unrec o r d e d , p r o b a b l y b e c a u s e t h e y are difficult t o m a n i p u l a t e and y i e l d little in the w a y o f s t r u c t u r a l detail. I n d i r e c t e v i d e n c e o f fungal a c t i v i t y has g e n e r a l l y n o t b e e n recognized. As a result, t h e diversity o f C a r b o n i f e r o u s fungi has b e e n u n d e r e s t i m a t e d , and t h e l i t e r a t u r e c o n t a i n s little d a t a t o facilitate f u r t h e r s t u d y . T h e a p p l i c a t i o n o f e l e c t r o n m i c r o s c o p y to the s t u d y o f fossil fungi p r o v i d e s a p o w e r f u l t o o l t h a t p r o m i s e s t o e x p a n d o u r k n o w l e d g e o f t h e s e o r g a n i s m s greatly. T h e p r e s e n t p a p e r describes s o m e fungal r e m a i n s discovered within the megaspores of a heterosporous, Carboniferous lycopod.
0034-6667/84/$03.00
© 1984 Elsevier Science Publishers B.V.
200 MATERIALS AND METHODS Permineralized fungal remains are f o u n d within coal balls from the wellknown Lewis Creek locality in southeastern K e n t u c k y (G ood and Taylor, 1970). Specimens come f r o m the Breathitt F o r m a t i o n which is early--middle Pennsylvanian (= Westphalian A--B equivalent) in age (G ood and Taylor, 1970; Phillips, 1980). A p p r o x i m a t e l y 25 specimens o f the l y c o p o d megaspore Triletes rugosus (Loose) S c h o p f contain spherical fungal bodies. Material was prepared f or light m i c r o s c o p y using standard coal ball techniques. In preparation for scanning electron microscopy, small portions o f the coal ball were removed, etched with dilute hydr oc h l ori c acid, and dried in an Autosamdri Critical Poi nt Drier. T he dried material was m o u n t e d on standard stubs, coated with gold, and examined on a Hitachi S-500 Scanning Electron Microscope. In preparation f or transmission electron m i croscopy, blocks were then treated with 10% sodium cyanide for approxi m at el y t w o hours to remove the gold, and cellulose acetate peels were subsequently made from t h e etched surfaces. Appropriate portions o f these peels were coated with agar on a millipore filter under suction. T h e y were then treated with 5% uranyl acetate, d ehydr a t e d, and e m b e d d e d in Spurr's Low Viscosity Plastic following standard techniques. E m b e d d e d specimens were sectioned and examined at 75 kV. Specimens bear collection numbers 1 0 7 2 8 - - 1 0 7 6 5 in The Ohio State University Paleobotanical Collections. DESCRIPTION Spherical bodies up to 70 pm in diameter are found within the l y c o p o d megaspore Triletes rugosus (Loose) Schopf. Megaspores are contained within intact cones o f F l e m i n g i t e s ( L e p i d o s t r o b u s ) schopfii Brack (Brack, 1970; Brack-Hanes and Thomas, 1983). Although t hey are well preserved, those spores invaded by fungi do not exhibit a distinct, well-preserved megag a m e t o p h y t e . Fungal specimens oc c ur singly (Plate I, 1, 5; Plate II, 3) or in close association with o t h e r similar structures (Plate I, 2--4). Although m a n y of the fungal bodies are free within the megaspore (Plate I, 1, 5; Plate II, 3), o t h e r are e m b e d d e d in a c o m p a c t stroma-like tissue (Plate I, 2--4). The spherical structures are smooth-walled and exhibit no evidence of papillae or o t h e r p r e f o r m e d germination sites. Their walls seem t o be at least t w o layers thick PLATE I 1. Triletes rugosus in section view with isolated fungal body (arrow). 2124 F Bot. #4.
× 100. 2. Sporangia embedded in stroma-like matrix. 2124 F Bot. #4. × 340. 3. Triletes rugosus containing fungal remains. Note hyphae on inside surface of megaspore wall (arrow). 2124 F. × 80. 4. Higher magnification of 3. Note sporangial walls. 2124 F. × 500. 5. Individual sporangium and associated stromatie tissue. Note small hollow area at left (arrow). 2124 F. × 600.
t
-3
.-t
202
in transmitted light, and layering is even more prominent at the ultrastructural level where four or five units are seen (Plate II, 2). There is some variability in the number of layers, suggesting possible preservational modification including degradation and shrinkage. Individual wall layers are solid and homogenous at the ultrastructural level (Plate II, 2). The amount of tissue associated with the fungal bodies varies considerably. In some specimens it is nearly absent, while in others it occupies approximately 60% of the interior of the spore. In transmitted light and scanning electron microscopy the tissue is usually amorphous (Plate I, 2, 4, 5). There is no evidence of intact, parenchymatous cells typical of preserved megagametophytic tissue. However, occasional small, round openings are visible (Plate I, 5) which may represent either hyphae in section view or immature fruiting structures. In one instance a fungal body is attached at two points to a hyphal strand which is continuous with the more loosely organized stroma-like material (Plate II, 5). This material is probably fungal in origin, at least in part, although it may also include fragments of degraded megagametophytic tissue. Other hyphaelike filaments are sometimes present along the inner surface of the megaspore wall (Plate I, 3; Plate II, 1). These strands are restricted to this area, and apparently do not ramify throughout the interior of the megaspore. These vary in diameter and are n o t easily seen in reflected light because of the sectional nature of the preparations. There is no physical connection between these filaments and other structures within the megaspore. DISCUSSION Like many undescribed fungi present in Pennsylvanian spores, the organisms within Triletes rugosus are relatively small and indistinct bodies which represent only a portion of one phase of the life cycle. They are assumed to be fungal in origin on the basis of their morphological similarity to other Carboniferous fungi, particularly fossil Glomus-like chlamydospores {Wagner and Taylor, 1982). The physical connection of the spherical bodies with hyphae-like strands strengthens this interpretation. To our knowledge comparable specimens have not been described from the fossil record. Although the present material resembles the Glomus-like chlamydospores found throughout the Paleozoic, it m a y be distinguished from fossil Glomus-like specimens on the basis of wall structure. Despite superficial similarities in the organization of the wan visible in transmitted light, differences are apparent at the ultrastructural level. The walls in the present material exhibit more layers than is typical of the fossil Glomus. The affinities of these specimens are presently indeterminable due primarily to the lack o f contents in the spheres. However, among extant forms they show some similarity to sporangia of chytridiaceous fungi or perhaps to the chlamydospores of oomycetes. Members of these groups were well established by the Pennsylvanian (see Tiffney and Barghoorn, 1974) and chytrids are associated with lycopods t o d a y (Sorokin, 1872; Zopf, 1887).
203
PLATE II
1. Higher m a g n i f i c a t i o n o f fungal h y p h a e seen o n m e g a s p o r e wall in Plate I, 3. 2 1 2 4 F. x 650. 2. S e c t i o n t h r o u g h sporangial wall s h o w i n g m u l t i p l e layers. I n n e r m o s t surface o f wall indic a t e d b y arrow. Bar r e p r e s e n t s 4 urn. D i r e c t i o n of s e c t i o n is parallel t o t h e bar scale. 2 1 2 4 F. X 5000. 3. I n d i v i d u a l fungal s p o r a n g i u m . 2 1 8 4 F. x 2000. 4. Higher m a g n i f i c a t i o n o f s t r o m a - l i k e tissue. 2 1 8 4 F. x 2000. 5. S p o r a n g i u m a t t a c h e d t o h y p h a l strand. 2 1 2 4 F Bot. #4. x 350.
204 ACKNOWLEDGMENTS
The authors wish to thank Ms. Kathleen Pigg who drew our attention to these organisms and Drs. Roland L. Seymour and Lennart Holm for useful discussion concerning their structure and affinities. This research was supported in part by funds from the National Science Foundation (DEB8213060). REFERENCES Baxter, R.W., 1960. Sporocarpon and allied genera from the American Pennsylvanian. Phytomorphology, 10 : 19--25. Baxter, R.W., 1975. Fossil fungi from American Pennsylvanian coal balls. Univ. Kansas Paleontol. Contrib., 77: 1--6. Batra, L.R., Segal, R.H. and Baxter, R.W., 1964. A new Middle Pennsylvanian fossil fungus. Am. J. Bot., 51: 991--095. Brack, S.D., 1970. On a new structurally preserved arborescent lycopsid fructification from the Lower Pennsylvanian o f North America. Am. J. Bot., 57: 317--330. Brack-Hanes, S.D. and Thomas, B.A., 1983. A re-examination of Lepidostrobus Brongniart. Bot. J. Linn. Soc., 86: 125--133. Davis, B. and Leisman, G.A., 1962. Further observations on Sporocarpon and allied genera. Bull. Torrey Bot. Club., 89: 97--109. Dennis, R.L., 1976. Palaeosclerotium, a Pennsylvanian age fungus combining features of modern Ascomycetes and Basidiomycetes. Science, 192 : 6 6 - 6 8 . Good, C.W. and Taylor, T.N., 1970. On the structure of Cordaites felicis Benson from the Lower Pennsylvanian o f North America. Palaeontology, 13 : 29--39. McLean, R.C., 1922. On the fossil genus Sporocarpon. Ann. Bot., 3 6 : 7 1 - - 9 0 (PI.VIII--X). Phillips, T.L., 1980. Stratigraphic and geographic occurrences of permineralized coalswamp plants -- Upper Carboniferous of North America and Europe. In: D.L. Dilcher and T.N. Taylor (Editors), Biostratigraphy o f Fossil Plants -- Successional and Palaeoecological Analysis. Dowden, Hutchinson and Ross, Stroudsburg, PA, pp.25--92. Rothwell, G.W., 1972. Palaeosclerotium pusillum gen. et sp. nov. : A fossil eumycete from the Pennsylvanian o f Illinois. Can. J. Bot., 50: 2353--2356. Sorokin, N., 1872. Mycological investigations. Tr. O.-Va. Jest-Ispyt., 2: 1--46. Stubblefield, S.P. and Taylor, T.N., 1983. Studies of Carboniferous fungi I. The structure and organization of Traquairia (Ascomycota). Am. J. Bot., 70: 387--399. Tiffney, B.H. and Barghoorn, E.S., 1974. The fossil record of the fungi. Occas. Pap. Farlow Herb. Cryptogam. Bot. Harv., 7 : 1--42. Wagner, C.A. and Taylor, T.N., 1982. Fungal chlamydospores from the Pennsylvanian of North America. Rev. Palaeobot. Palynol., 37 : 317--328. Williamson, W.C., 1880. On the organization of the fossil plants of the Coal-measures -Part 10. Including an examination o f the supposed radiolarians of the Carboniferous rocks. Philos. Trans. R. Soc. Lond., 171 : 493--539. Zopf, W., 1887. Ueber einige niedere Algenpilze (Phycomyceten) und eine neue Methode ihre Keime aus den Wasser zu isolieren. Abh. Naturforsch. Ges. Halle, 17: 77--107.