Sara P. Stubblefield

Fossil Mycorrhizae: A Case for Symbiosis

Vesicular-arbuscular mycorrhizae are significant in the physiology and ecology of extant vascular plants, and they may also have played a major role in the origin of the vascular land flora. The case for fossil vesicular-arbuscular mycorrhizae rests upon hyphae and chlamydospore-like bodies in several Paleozoic taxa, but fossil arbuscles are unknown to date. Specimens from the Triassic of Antarctica represent the first known occurrence of arbuscles in the fossil record.

Studies of Paleozoic fungi. IV. Wall ultrastructure of fossil endogonaceous chlamydospores

Fossil endogonaceous chlamydospores are described from the aerial axes and roots of several Paleozoic plants preserved in calcilutite nodules and calcareous coal balls. Specimens come from six Paleozoic localities extending from the uppermost Lower Devonian through the Upper Pennsylvanian. Although fossil chlamydospores are markedly similar to the mod? ern Endogonaceae in transmitted light, ultrastructural comparisons have not previously been made. The fine structure of the walls of these spores is consistent with past interpretations which relate them to the modern Endogonaceae, but thorough comparisons cannot be made due to the lack of comparable ultrastructural information from extant VA mycorrhizae. The evidence from mycorrhizal associations in the fossil record is evaluated. The presence of fungal chlamydospores in permineralized Paleozoic plants has been noted repeatedly since the early 1900s. Such structures are probably best known from the Devonian Rhynie Chert (Kidston and Lang, 1921), and have aroused considerable interest because of their resemblance to extant vesiculararbuscular (VA) mycorrhizal fungi. Butler (1939) was perhaps the first to suggest that such bodies were fossil representatives of the modern Endogonaceae, while others have reported similar fungi and considered the possibility of endomycorrhizal relationships in the Paleozoic (Weiss, 1904; Lignier, 1906; Osborn, 1909; Halket, 1930; Zimmermann, 1933; Andrews and Lenz, 1943; Wolf and Wolf, 1947; Kelly, 1950; Boullard and Lemoigne, 1971). More recently, Pirozynski and Malloch (1975) have argued for the presence of VA mycorrhizae associated with plants in the Paleozoic, and have suggested that the establishment of mycorrhizal relationships was a major factor in the development of the vascular land flora. We can evaluate this suggestion only insofar as it is possible to recognize fossil mycorrhizae and distinguish them from other root endophytes (Berch and Ken? drick, 1982). In the past, comparisons have been made primarily through light microscopy and have centered on gross morphological detail. The use of scanning and transmission electron microscopy provides an opportunity to make ultra? structural comparisons as well, particularly with respect to the wall structure of chlamydospores. The relevance of wall structure to questions of fungal phylogeny and the

GEOTRICHITES GLAESARIUS, A CONIDIAL FUNGUS FROM TERTIARY DOMINICAN AMBER

Geotrichites glaesarius, a. new fungal anamorph, is described from Dominican amber of late Oligocene or early Miocene age. A well-developed mycelium is present on the surface of an arachnid cadaver; hyphae are not present in the body cavity. Septate hyphae are either erect or decumbent, and extensively branched. Oblong arthroconidia are borne terminally on undifferentiated hyphae. Conidiogenesis appears to be ofthe holoarthric type with conidia sometimes joined by narrow connectives. The fungus is apparently saprophytic and resembles several modern moniliaceous fungi, particularly Geotrichum candidum.

A possible endogonaceous fungus from the Triassic of Antarctica

Walker, C. 1983. Taxonomic concepts in the Endogonaceae; spore wall characteristics in species descriptions. Mycotaxon 18: 443-455. , and F. E. Sanders. 1986. Taxonomic concepts in the Endogonaceae. III. The separation of the genus Gigaspora Gerd. & Trappe into two genera, Gigaspora and Scutellospora. Mycotaxon 27: 169-182. Woodhouse, W. W., E. D. Seneca, and A. W. Cooper. 1968. Use of sea oats for dune stabilization in the southeast. Shore Beach 36: 15-21. , igaspora and Scutellospora. Mycotaxon 27:

Fungal remains in the lycopod megaspore Triletes rugosus (Loose) schopf

Abstract Spherical fungal bodies within the lycopol megaspore Triletes rugosus are described from permineralized plant remains of Pennsylvanian age. Specimens reach 70 μm 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 Glomus -like 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.

Compressed plants from the lower Pennsylvanian of Kentucky (U.S.A.). I. Crossotheca Kentuckiensis N. Sp.

Stubblefield, S.P., Taylor, T.N. and Daghlian, C.P., 1982. Compressed plants from the Lower Pennsylvanian of Kentucky (U.S.A.). I. Crossotheca kentuekiensis n. sp. Rev. Palaeobot. Palynol., 36: 197--204. A new species of Crossotheca is described from the Lewis Creek locality in eastern Kentucky, U.S.A. Branching systems bear both vegetative and fertile pinnae, and exhibit many characteristics of the presumed lyginopterid pollen organ Feraxotheca. Ultimate fertile pinnae each terminate in a round--oval pad of tissue which bears 4--6 elongate, pendant sporangia. Microspores are circular--oval and trilete ; ornamentation consists of small, uniformly spaced grana. Vegetative pinnae produce short, deeply lobed pinnules with narrow, rounded segments. Extensive morphological similarities suggest a close relationship between the petrified pollen organ Feraxotheca and the new species of Crossotheca.