Ascocarp Wall Research Articles

Perithecial ascomycetes from the 400 million year old Rhynie chert: an example of ancestral polymorphism

We describe a perithecial, pleomorphic ascomycetous fungus from the Early Devonian (400 mya) Rhynie chert; the fungus occurs in the cortex just beneath the epidermis of aerial stems and rhizomes of the vascular plant Asteroxylon. Perithecia are nearly spherical with a short, ostiolate neck that extends into a substomatal chamber of the host plant; periphyses line the inner surface of the ostiole. The ascocarp wall is multilayered and formed of septate hyphae; extending from the inner surface are elongate asci interspersed with delicate paraphyses. Asci appear to be unitunicate and contain up to 16 smooth, uniseriate-biseriate ascospores. The method of ascospore liberation is unknown; however, the tip of the ascus is characterized by a narrow, slightly elevated circular collar. Ascospores appear 1–5 celled, and germination is from one end of the spore. Also present along the stems and interspersed among the perithecia are acervuli of conidiophores that are interpreted as the anamorph of the fungus. Conidiogenesis is thallic, basipetal and probably of the holoarthric-type; arthrospores are cube-shaped. Some perithecia contain mycoparasites in the form of hyphae and thick-walled spores of various sizes. The structure and morphology of the fossil fungus is compared with modern ascomycetes that produce perithecial ascocarps, and characters that define the fungus are considered in the context of ascomycete phylogeny.

Perithecial ascomycetes from the 400 million year old Rhynie chert: an example of ancestral polymorphism

We describe a perithecial, pleomorphic ascomycetous fungus from the Early Devonian (400 mya) Rhynie chert; the fungus occurs in the cortex just beneath the epidermis of aerial stems and rhizomes of the vascular plant Asteroxylon. Perithecia are nearly spherical with a short, ostiolate neck that extends into a substomatal chamber of the host plant; periphyses line the inner surface of the ostiole. The ascocarp wall is multilayered and formed of septate hyphae; extending from the inner surface are elongate asci interspersed with delicate paraphyses. Asci appear to be unitunicate and contain up to 16 smooth, uniseriate-biseriate ascospores. The method of ascospore liberation is unknown; however, the tip of the ascus is characterized by a narrow, slightly elevated circular collar. Ascospores appear 1-5 celled, and germination is from one end of the spore. Also present along the stems and interspersed among the perithecia are acervuli of conidiophores that are interpreted as the anamorph of the fungus. Conidiogenesis is thallic, basipetal and probably of the holoarthric-type; arthrospores are cube-shaped. Some perithecia contain mycoparasites in the form of hyphae and thick-walled spores of various sizes. The structure and morphology of the fossil fungus is compared with modern ascomycetes that produce perithecial ascocarps, and characters that define the fungus are considered in the context of ascomycete phylogeny.

Article retracted due to printing error -- Please see issue 97:1 for the correct version of "Perithecial ascomycetes from the 400 million year old Rhynie chert: an example of ancestral polymorphism"

We describe a perithecial, pleomorphic ascomycetous fungus from 400 MaBP Early Devonian (400 mya) Rhynie chert; the fungus occurs in the cortex just beneath the epidermis of aerial stems and rhizomes of the vascular plant Asteroxylon. Perithecia are nearly spherical with a short, ostiolate neck that extends into a substomatal chamber of the host plant; periphyses line the inner surface of the ostiole. The ascocarp wall is multilayered and formed of septate hyphae; extending from the inner surface are elongate asci interspersed with delicate paraphyses. Asci appear to be unitunicate and contain up to 16 smooth, uniseriate-biseriate ascospores. The method of ascospore liberation is unknown; however, the tip of the ascus is characterized by a narrow, slightly elevated circular collar. Ascospores appear 1–5 celled, and germination is from one end of the spore. Also present along the stems and interspersed among the perithecia are acervuli of conidiophores that are interpreted as the anamorph of the fungus. Conidiogenesis is thallic, basipetal and probably of the holoarthric-type; arthrospores are cube-shaped. Some perithecia contain mycoparasites in the form of hyphae and thick-walled spores of various sizes. The structure and morphology of the fossil fungus is compared with modern ascomycetes that produce perithecial ascocarps, and characters that define the fungus are considered in the context of ascomycete phylogeny.

A Method for Sectioning Ascomycete Herbarium Specimens for Light Microscopy

(1991). A Method for Sectioning Ascomycete Herbarium Specimens for Light Microscopy. Mycologia: Vol. 83, No. 4, pp. 520-524.

Ascocarp Dehiscence and Ascospore Discharge inUncinula necator

In this study, we describe some of the anatomical, cytological, and physiological changes that precede deshiscence of cleistothecia of U.n., we report on cytoplasmic water potential and strength of the ascocarp wall during overwintering, and report the effects of temperature and wetting upon the mechanism of ascocarp dehiscence and ascospore discharge under controlled conditions and in vineyards

Germination of Ascospores and Infection ofVitisbyUncinula necator

Ascospores of Uncinula necator were released from cleistothecia periodically from November (leaf fall) to May (bud break) by fracturing the ascocarp wall and allowing the spores to be discharged onto glass slides. Water potential of ascospore cytoplasm decreased continuously during this period. Ascospores did not germinate before November. Thereafter (until April), ascospores germinated only in the presence of free water but frequently burst in water, presumably because of high pressure potentials within the spore (...)

Development and Cytology of Anixiella endodonta

The homothallic fungus Anixiella endodonta exhibits typical sordariaceous centrum development. The ascocarp begins development as a coiled or looped ascogonium that becomes surrounded by hyphal branches. The surrounding hyphae produce the ascocarp wall and all the nonascogenous elements of the centrum. A cavity forms within the centrum. Paraphyses grow upward into the cavity prior to ascus formation and disappear as the asci enlarge. Crozier formation, ascus production, and cytology within the ascus follow the typical pattern. A diffuse diplotene stage is included. Unusually large spindle pole bodies are striking elements of the interphase II nucleus. The haploid chromosome number is six. The development and cytology of A. endodonia is compared with that of previously studied species of Anixiella and Gelasinospora. Similarities and differences indicate that the two genera are clearly related but are sufficiently distinct to warrant segregation.

ADDITIONAL SPECIES OF PODODIMERIA (LOCULOASCOMYCETES)

Pododimeria, containing the brown‐spored species P. gallica and P. andina, is expanded to include species with hyaline as well as brown ascospores. Two new hyalodidymous taxa, P. juniperi and P. gelatinosa, are added to the genus. Species of Pododimeria occur as ectocommensals on living shoots of Cupressaceae or Podocarpaceae. Although the superficial mycelium may extend into the labyrinthine chambers enclosed by the imbricated scale leaves of the host, it does not penetrate the cuticle. The tiny, black, subglobose, uniloculate ascocarps taper basally to stromatic stipes. The bitunicate asci are interspersed with pseudoparaphyses composed of broad, irregularly shaped cells that readily break apart. The thick, brown to bluish‐green ascocarp wall of P. juniperi has a broad equatorial band of prosenchymatous cells. The ascocarp wall of P. gelatinosa is composed uniformly of subhyaline, gelatinous pseudoparenchymatous cells covered by a dark, amorphous crust.

MORPHOLOGICAL STUDIES IN PODOSPORA ANSERINA

Perithecium development in Podospora anserina begins with the formation of a coiled ascogonial initial that arises as a lateral branch from a vegetative hypha. Hyphae grow up around the initial, forming an envelope that will become the ascocarp wall. As the ascocarp increases in size, several layers of thin‐walled pseudoparenchyma cells form inside the wall, especially at the apex of the ascocarp. Paraphyses arise both from the base of the ascocarp and from the innermost layer of pseudoparenchyma cells and grow inward and upward, completely filling the centrum with tightly packed filaments. During development of the ascocarp the ascogonium proliferates to form ascogenous hyphae along the base of the centrum. Asci arise from the ascogenous hyphae and grow up among the paraphyses. Meristematic growth at the ascocarp apex results in the formation of an ostiole lined with periphyses. Centrum structure in P. anserina could be interpreted as intermediate between the Xylaria and Diaporthe types.

Morphological Studies in Podospora anserina

Perithecium development in Podospora anserina begins with the formation of a coiled ascogonial initial that arises as a lateral branch from a vegetative hypha. Hyphae grow up around the initial, forming an envelope that will become the ascocarp wall. As the ascocarp increases in size, several layers of thin-walled pseudoparenchyma cells form inside the wall, especially at the apex of the ascocarp. Paraphyses arise both from the base of the ascocarp and from the innermost layer of pseudoparenchyma cells and grow inward and upward, completely filling the centrum with tightly packed filaments. During development of the ascocarp the ascogonium proliferates to form ascogenous hyphae along the base of the centrum. Asci arise from the ascogenous hyphae and grow up among the paraphyses. Meristematic growth at the ascocarp apex results in the formation of an ostiole lined with periphyses. Centrum structure in P. anserina could be interpreted as intermediate between the Xylaria and Diaporthe types.

The Centrum of the Sooty Mold Ascomycete Limacinula samoensis

Centrum development in the sooty mold Ascomycete Limacinula samoensis von Hoehnel emend. Reynolds proceeds in an ascostroma which begins as a small cushion of somatic tissue and enlarges by multiplication of cells in an apical region and by cell enlargement. A two-layered ascocarp wall initially surrounds a pseudoparenchymatous core into which the bitunicate asci protrude. Interascal strands of pseudoparenchymatous tissue disintegrate at maturity of the ascocarp. An apical meristem eventually culminates activity with formation of a short ostiolate neck. Centrum development is homologous to the Dothidea type. The centrum development of other capnodiaceous fungi is reviewed.

THE CENTRUM OF THE SOOTY MOLD ASCOMYCETE LIMACINULA SAMOENSIS

Centrum development in the sooty mold Ascomycete Limacinula samoensis von Hoehnel emend. Reynolds proceeds in an ascostroma which begins as a small cushion of somatic tissue and enlarges by multiplication of cells in an apical region and by cell enlargement. A two‐layered ascocarp wall initially surrounds a pseudoparenchymatous core into which the bitunicate asci protrude. Interascal strands of pseudoparenchymatous tissue disintegrate at maturity of the ascocarp. An apical meristem eventually culminates activity with formation of a short ostiolate neck. Centrum development is homologous to the Dothidea type. The centrum development of other capnodiaceous fungi is reviewed.

Ascocarp Development in Two Homothallic Neurosporas

Perithecia of Neurospora terricola and N. dodgei are initiated by the formation of a coiled archicarp, the terminal portion of which is soon differentiated as an ascogonium consisting of several cells. Sterile hyphae which early envelop the female organ give rise to the ascocarp wall. No trichogynes were identified. When the protoperithecium of N. terricola has reached a diameter of approximately 100 /u and that of N. dodgei about 160 u, primary ascogenous hyphae start to develop from the ascogonium. Immediately above these a centrum cavity appears into which paraphyses quickly grow. Asci do not appear until the centrum has attained nearly its maximum size and an ostiolar canal has been formed. As the asci develop, the paraphyses disintegrate. It is concluded that the perithecial centrum is of the "Xylariatype," as defined by Luttrell, and that Neurospora should therefore be placed in the Xylariales in the Luttrell scheme of classification. In many morphological and cytological features, N. terricola and N. dodgei resemble closely not only other species of Neurospora previously studied but also other members of the Sordariaceae (sensu Moreau), particularly members of the genera Gelasinospora, Sordaria, and Pleurage. Noteworthy cytological features encountered were: multinucleate ascogonial cells; ascospores initially uninucleate but becoming binucleate prior to maturation; in N. terricola beaked nuclei bearing prominent appendages at the 4-nucleate stage of ascus development; and a haploid chromosome number of 7 in N. terricola.

Hypoxylon fuscum. II. Developmental Morphology on Alnus tenuifolia

Hyphae of Hypoxylon fuscum invade alder wood and attack all cell types. Eventually, hyphae emerge into the bark, rupture the periderm, and form a stroma. Coiled ascogonia are produced in the stroma. Each ascogonium becomes ensheathed in a hyphal envelope which ultimately develops into the ascocarp wall. The ascogonium becomes segmented, falling apart into cells. Some ascogonial cells produce ascogenous cells; others become inflated and branched. Polar growth of the envelope and filamentous space-making hyphae are involved in perithecial expansion. Developing asci grow into the mass of space-making hyphae and lyse some of it. The developmental patternis of the Xylaria type.

GENERIC CORRELATIONS AND CONCEPTS: GRIPHOSPHAERIOMA AND LABRIDELLA

The connection of the type species of Griphosphaerioma von Höhnel with its conidial state, the type species of Labridella Brenckle was accepted. Griphosphaerioma kansensis (Ell. & Ev.) n. comb. (= G. symphoricarpi Rehm ex von Höhnel) lias unitunicate asci, with a pulvillus, but, unlike the type species of Griphosphaeria and Clathridium, without an amyloid ring. The conidial state of Griphosphaerioma unlike the conidial states of Griphosphaeria and Clathridium produces only one conidium on each conidiophore. The Labridella conidial state is segregated from Pestalotia de Notaris as Labridella comu-cervae Brenckle because of its unique conidia and the manner of their formation.The pyrenomycete first described as Plowrightia symphoricarpi Ell. & Ev. associated on Symphoricarpos with Griphosphaerioma and sometimes confused with it, but distinguished by bitunicate asci, phaeodidymous ascospores, and a pseudoparenchymatous ascocarp wall is renamed Gibbera andersonii. A revised synonymy, illustrations, and a description are provided for both species.

MORPHOLOGY OF NEURONECTRIA PEZIZA

Hanlin, Richabd T. (Georgia Expt. Sta., Experiment.) Morphology of Neuroneetria peziza. Amer. Jour. Bot. 60(1): 56–66. Illus. 1963.—Swollen tips of vegetative hyphae develop into multicellular, multinucleate ascogonia. Hyphae grow up to form a pseudoparenchymatous ascocarp wall. The ascogonia give rise to ascogenous cells from which croziers and asci form. As the ascocarp develops, an apical meristem produces many cells which are pushed downward and form a compact pseudoparenchyma in the centrum. As the asci form, the cells of the pseudoparenchyma elongate, forming central strands. These disintegrate as the asci grow up among them. Mature asci possess a thickened apical cap but no apical ring; the ascospores have longitudinal striations. The chromosome number is n = 5. The pattern of development resembles the Diapor the type of Luttrell but is unique in the formation of strands from the pseudoparenchyma. Other characters, however, indicate a closer affinity to Nectria.

A New Genus of the Eurotiales

In the course of an investigation on the fungi of Lahore soils, a member of the Eurotiales was repeatedly isolated at different soil depths. It has Thielavia-like ascospores but its peridium is colorless, an unusual feature in the Eurotiales and Perisporiales. A culture of this fungus was sent to the Commonwealth Mycological Institute for advice and Dr. C. Booth replied Culture M4 (83279) should I think be placed in a new genus differing from Thielavia in the ascocarp wall. In accordance with this suggestion, the fungus is here described as the type of a new genus.

The Development of the Ascocarp of Acrospermum Compressum

The genus Acrospermum was founded by Tode (1790) with A. compressum as the type species. Rehm (1887) considered the genus as one of the Hysteriales. Ellis and Everhart (1892) transferred it from that order to the Hypocreales. The family Acrospermaceae was erected for the genus by Lindau (1896) who incorporated it tentatively in the Hysteriales. Von Hohnel (1917), regarding the fungus as undoubtedly pyrenomycetous, placed it in the Sordariaceae of the Sphaeriales. Riddle (1920), who studied the internal structure of the mature ascocarp in stained paraffin sections, concluded that the genus was clearly re? lated to the Hypocreales, it being obviously similar to them in texture and coloration. Clements and Shear (1931) follow Ellis and Everhart and Riddle in considering Acrospermum as one of the Hypocreales. Arnaud (1930) recently added one more taxonomic position for consideration, namely, that of the Caliciees, a discomycetous group treated by him as closely related to the Coryneliales. These several divergent points of view, with the exception of that of Riddle, were based chiefly on the superficial appearance of the fruit-body. As the taxonomic position of Acrospermum is clearly in doubt, and as its possible relationship to the Coryneliales is of interest in connection with researches in progress on that group, the present investigation was suggested by Professor Fitzpatrick. Emphasis has been placed by us upon the nature and origin of the ascocarp wall and ascigerous cavity, the initiation and development of the asci, and the shape and character of the ostiolar opening.