DEVELOPMENT OF THE PERITHECIUM IN GNOMONIA COMARI (DIAPORTHACEAE)

Perithecia of Gnomonia comari (Ascomycetes) mature within 14 days on cornmeal agar under continuous fluorescent light at 25 C. The perithecium is initiated by a coiled, multicellular ascogonium. Branches from somatic hyphae surround the ascogonium. This hyphal envelope early differentiates into two regions: a centrum of pseudoparenchymatous cells and a peripheral wall of more elongated, flattened cells. The wall produces a long, ostiolate beak by eruption of a column of hyphae from the inner layers at the apex; the cells gradually become thick-walled and brown from the peripheral layers inward. Proliferations from the ascogonial cells near the center of the perithecium form a bowl-shaped mass of ascogenous hyphae which expands centrifugally until it appears in section as a crescentic layer across the middle of the centrum. The centrum pseudoparenchyma above this incipient hymenium disintegrates, and short abortive paraphyses extend upward from the subhymenial pseudoparenchyma into the resulting cavity. The paraphyses disintegrate as the asci develop among them. The hymenium gradually pushes downward into the disintegrating subhymenial pseudoparenchyma until it rests on the perithecial wall. Maturing asci become detached from the hymenium, fill the perithecial cavity, and pass through the ostiole. At the tip of the beak they discharge their ascospores forcibly. Diaporthaceae with abortive paraphyses may occupy an intermediate position in a series leading from forms (Gaeumannomyces graminis) with long delicate paraphyses resembling those in the Sordariaceae to forms (Stegophora ulmea) in which the centrum is entirely pseudoparenchymatous.     

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.     

CENTRUM DEVELOPMENT IN DIDYMELLA BRYONIAE

Early stages of pseudothecium development consist of small pseudoparenchymatous stromata in which ascogonia differentiate. Deeply staining cells in the apical region of the young pseudothecium elongate to form pseudoparaphyses, which grow down to fill the centrum. Ascogenous hyphae grow out from ascogenous cells, located in the basal plectenchyma, and croziers arise and proliferate from the ascogenous hyphae. Bitunicate asci grow up among the pseudoparaphyses and forcibly discharge two-celled hyaline ascospores at maturity. Because centrum development in Didymella bryoniae (Auersw.) Rehm is pseudoparaphysate, the causal agent of gummy stem blight in watermelon is properly placed in the order Pleosporales. The placement of this species in Didymella on the basis of the Ascochyta cucumis Fautr. et Roum. anamorph is supported by centrum structure.     

The morphology of Cercophora palmicola (Lasiosphaeriaceae)

A detailed study of ascomal morphology and development in Cercophora palmicola showed that ontogeny is ascohymeniaceous, giving rise to an ostiolate perithecium. Ascomal initials consist of a coiled ascogonium surrounded by several layers of hyphae whose cells become pseudoparenchymatous. The centrum of the young ascoma is composed of a few rows of large, thin-walled pseudoparenchymatous cells that line the ascomal wall, with the central region filled by tightly packed, filamentous paraphyses. The ascogenous system forms along the inside of the layer of pseudoparenchymatous cells at the base of the paraphyses and gives rise to unitunicate asci that grow up among the paraphyses. The wall of the mature perithecium is greatly thickened. It is composed of three regions: a thin outer region of darkly pigmented, angular cells with thickened walls; a broad central region of cells with gelatinized walls; and a thin inner region of flattened cells. Ascomal ontogeny in C. palmicola conforms well to the Sordaria type of development, as defined by Huang.     

STUDIES IN THE GENUS NECTRIA. II. MORPHOLOGY OF N. GLIOCLADIOIDES

Hanlin , Richard T. (Georgia Experiment Station, Experiment.) Studies in the genus Nectria. II. Morphology of N. gliocladioides. Amer. Jour. Bot. 48(10): 900–908. Illus. 1961.—Swollen tips of vegetative hyphae develop into multicellular archicarps from which multinucleate ascogonia form. From basal cells of each archicarp arise hyphae which grow up into a prosenchymatous, true perithecial wall; around this wall is formed a thin pseudoparenchymatous stroma of compacted hyphae. The ascogonia give rise to ascogenous cells from which croziers and asci form directly. At the same time, an apical meristem forms cells that grow downward into the centrum. These are pseudoparaphyses. Asci grow up among the pseudoparaphyses, which deliquesce as the ascocarp matures. The ascus tip contains a thick ring with a pore and lateral thickening of the ascus wall. Ascospores are forcibly ejected. The chromosome number is 4. This species conforms to the Nectria Developmental Type of Luttrell.     

MORPHOLOGY OF NECTRIA HAEMATOCOCCA

Ascocarp development in Nectria haematoccocca begins with the formation of deeply staining coils as lateral branches of the vegetative hyphae. As these coils develop into multicellular, multi-nucleate ascogonia, they are surrounded by a pseudoparenchymatous envelope. During ascocarp development an apical meristem produces cells that elongate downward into the centrum, forming long, filamentous, apical paraphyses. When fully developed the cells of the apical paraphyses swell, producing a tissue that is pseudoparenchymatous in appearance. The ascogonium proliferates to form a layer of multinucleate ascogenous cells across the base of the ascocarp. Asci form from the ascogenous cells by means of croziers. The asci grow up among the apical paraphyses, which disintegrate as the ascocarp matures. This pattern is typical of the Nectria-type of development, indicating that this species belongs in the Hypocreales.     

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.     

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.     

MORPHOLOGY OF CHAETOMIUM ERRATICUM

Development of perithecia from single, uninucleate ascospores disclosed a homothallic condition for Chaetomium erraticum. This species was found to produce sessile ascogonial coil initials from uninucleate vegetative cells that become enveloped by hyphae formed at the base of the ascogonium. The ascogonium consists of several cells that are uninucleate or binucleate. A perithecium forms from numerous divisions and enlargement of the surrounding uninucleate cells. Differentiation of the perithecial cells results in the formation of a carbonaceous wall, perithecial hairs, and an ostiole lined with periphyses. A convex hymenial cluster of ascogenous cells forms in the lower half of the centrum from which typical croziers develop. Asci push up into the pseudoparenchyma cells of the centrum. The growth of the ascogenous system is in part responsible for increase in perithecial size. The breakdown of the pseudoparenchyma cells around the developing asci results in the formation of a central cavity in which ascospores are released when the asci deliquesce. No paraphyses are present. The type of development and features of the centrum of C. erraticum and other species of Chaetomium indicate a distinct Xylaria-type centrum.     

THE DEVELOPMENT AND CYTOLOGY OF PYCNIDIOPHORA DISPERSA

Ascocarp development in Pycnidiophora dispersa is similar to that in Phaeotrichum. A stroma originates in an intercalary position on a hypha. It increases in size, and the outer cell layer differentiates to form the wall. The ascogenous system forms from a mass of fertile cells in the center of the centrum. These become enlarged and multinucleate and give rise to ascogenous hyphae which form asci at their tips by means of croziers. In time, most of the cells of the centrum become fertile and give rise to ascogenous hyphae. There are no sterile threads in the centrum and no hymenium is present, the asci being scattered throughout the locule. The haploid chromosome number is n = 6.     

THE MORPHOLOGY AND CYTOLOGY OF PREUSSIA FUNICULATA

The vegetative nuclei of Preussia funiculata (Preuss) Fuckel appear to divide in two ways. One is very similar to mitosis in higher plants except that no typical metaphase is present. The other consists of elongated nuclei splitting longitudinally into two halves. Ascocarp development is similar to that found in the Pleosporales. A stroma originates in an intercalary position on a hypha. It increases in size, and the outer cell layers differentiate to form the wall. The ascogenous system arises from multinucleate ascogonial cells scattered throughout the centrum. These give rise to large, lobate, multinucleate cells which in time form asci by means of croziers. The mature centrum contains a distinct hymenium and paraphysoids. The haploid chromosome number appears to be 12.     

Bambusicolous fungi in Japan (6): Katumotoa, a new genus of phaeosphaeriaceous ascomycetes

A new genus, Katumotoa, is established for a single species, K. bambusicola, collected from culms of Sasa kurilensis. Morphological differences between Katumotoa and some related genera are noted. Katumotoa is characterized by perithecioid ascomata, thin ascomal wall composed of small pseudoparenchymatous cells, cellular pseudoparaphyses, fissitunicate asci, and apiosporous fusiform ascospores with bipolar mucilaginous sheath. From these features, it is considered that the genus belongs to Phaeosphaeriaceae in Pleosporales.     

Perithecium development in Sordaria brevicollis

Microconidia and ascogonial coils were produced by the two strains of Sordaria brevicollis , WTA and WTa. Over 90% of the microconidia, which functioned chiefly for sexual reproduction, germinated producing short–lived germ tubes. Ascogonial coils with conspicuous trichogynes were observed. A hypha was initiated from the base of the ascogonial coil and soon completely surrounded it, giving rise to the protoperithecium. The ascogonial coil became the ascogonium within the proto–perithecium, and it was surrounded by a pseudoparenchymatous centrum. Many paraphyses arose from pseudoparenchymatous cells. The ascogonium followed the Sordariaceous type of development and gave rise to ascogenous hyphae, croziers, unitunicate asci and ascospores. Anomalous perithecia were observed and perithecia reached maturity 9–1 1 days after inoculation.     

ULTRASTRUCTURE OF ASCOCARP DEVELOPMENT IN SPORORMIA AUSTRALIS

Thin sections taken from intact ascocarps were examined to trace the developmental sequence of ascocarp formation in Sporormia australis Speg. The ascocarp originated from a uninucleate vegetative hyphal cell which underwent repeated divisions and formed an ascostroma. In the center of the young ascostroma a cavity formed, apparently from cell disintegrations, and enlarged as the ascocarp enlarged. Within the cavity pseudoparaphyses developed from undifferentiated pseudoparenchymatous cells at the apex of the cavity and extended downward. Ascogenous hyphae arose from proliferating uninucleate cells at the base of the cavity. As the ascocarp matured, the pseudoparenchymatous cells differentiated into three layers, none of which were considered homologous to the perithecial wall lining the cavity of pyrenomycetes. The cells of the apex were not differentiated into layers and light microscopy revealed the presence of an ostiole through which bitunicate asci discharged their eight 4-celled ascospores.     

ASCOCARPIC CENTRUM ONTOGENY OF SPECIES OF HYPODERMATACEAE OF CONIFERS. II

Ascocarpic studies of the ontogeny of Lophodermium nitens disclosed a type of development unlike that of all other species of Hypodermataceae occurring on conifer needles. For this reason the centrum of L. nitens is designated as Type III and is compared with Type I (Gordon, 1966). Because L. nitens produces its ascocarp in several tissues of various species of pine, the ontogeny of ascocarps in different locations is discussed and illustrated. The most significant ontogenetic feature of the ascocarp of L. nitens is a layer of hyaline cells in the primordium; this layer is meristematic and gives rise to all subsequent structures of the centrum.     

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.     

A REINTERPRETATION OF THE ONTOGENY OF THE ASCOCARP OF SPECIES OF THE ERYSIPHACEAE

A study of four species of Erysiphaceae (Uncinula salicis, Podosphaera leucotricha, Erysiphe cichoracearum, and Microsphaera diffusa) revealed that the binucleate stages of the ascocarp are initiated in a similar manner to those of Diporotheca rhizophila Gordon & Shaw. The “appendages” developing on immature ascocarps are considered to be receptive hyphae. Appendages characteristic of mature ascocarps are produced much later. Lysis of certain centrum cells occurs, and asci are initiated from some of the remaining binucleate centrum cells. Resorption of centrum cells by the asci is supported by this investigation, corroborating Björling's earlier studies on Erysiphe graminis.     

Stellatospora,a new genus of the Sordariaceae

In the course of study of fungi from soil, a new genus and species,Stellatospora terricola, was isolated. The fungus is distinguished from other known genera in having star- or comfit-shaped ascospores with a distinct germ pore. The morphological characters of the genus are considered to resemble those of the Sordariaceae in Ascomycotina.     

Ectomycorrhizae of Tomentella albomarginata (Thelephoraceae) on Scots pine

 The ectomycorrhizae of Tomentella albomarginata are comprehensively described and compared to ectomycorrhizae of other Tomentella species and to ectomycorrhizae of some members of Thelephoraceae ss. Stalpers and Bankeraceae ss. Stalpers. The ectomycorrhizae of T. albomarginata are characterized by a hyphal net lying on a pseudoparenchymatous mantle surface, by tubular outgrowths of irregularly angular mantle cells, and by clamp-bearing emanating hyphae. Accepted: 15 July 1995     

Reevaluation of the caudal skeleton of some actinopterygian fishes: II. Hiodon,Elops, and Albula

The vertebral centra of Hiodon, Elops, and Albula are direct perichordal ossifications (autocentra) which enclose the arcocentra as in Amia. An inner ring of ovoid cells forms in late ontogeny from the intervertebral space inside the autocentrum. The chordacentrum is reduced or completely absent in centra of adult Elops, whereas it forms an important portion of the centra in adult Hiodon. The posterior portion of the compound ural centrum 3+4+5 is partially (Hiodon) or fully formed by the chordacentrum (Elops, Albula). The haemal arches and hypurals are fused medially by cartilage or bone trabecles of the arcocentrum with the centra, even though they appear autogenous in lateral view in Elops and Albula. The composition of the caudal skeleton of fossil teleosts and the ontogeny of that of Hiodon, Elops, and Albula corroborate a one-to-one relationship of ural centra with these dorsal and ventral elements. The first epural (epural 1) of Elops relates to ural centrum 1, whereas the first epural (epural 2) of Hiodon and Albula relates to ural centrum 2. In Albula, the first ural centrum is formed by ural centrum 2 only. With 4 uroneurals Hiodon has the highest number within recent teleosts. Juvenile specimens of Hiodon have eight, the highest number of hypurals within recent teleosts; this is the primitive condition by comparison with other teleosts and pholidophorids. Reduction of elements in the caudal skeleton is an advanced feature as seen within elopomorphs from Elops to Albula. Such reductions and fusions occur in osteoglossomorphs also, but the lack of epurals and uroneurals separates most osteoglossomorphs (except Hiodon) from all other teleosts.