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.     

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.     

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.     

DEVELOPMENT OF THE ASCOCARP OF CERATOCYSTIS ULMI

Rosinski , Martin A. (U. Maine, Orono.) Development of the ascocarp of Ceratocystis ulmi. Amer. Jour. Bot. 48(4): 285–293. Illus. 1961.—A study of the development of the perithecium of Ceratocystis ulmi was conducted using classic histological techniques. This study revealed the presence of a singular combination of primitive and advanced characteristics. The perithecium possesses a simple centrum made up only of ascogenous hyphae and small, spherical asci, but croziers are formed prior to ascus formation, and the ascogenous hyphae are arranged in a hymenium. Since development of C. ulmi compares closely with most other accounts of development in other members of the genus Ceratocystis, it appears that Ceratocystis is a good taxon. In addition, because of its intermediate nature and because Ceratocystis is the type genus of the family Ophiostomataceae, this family should be placed in a separate order, the Ophiostomatales.     

MORPHOLOGY OF HYPOMYCES TRICHOTHECOIDES

Large, spirally coiled initials embedded in a subiculum develop into multicellular, multinucleate ascogonia. Hyphae grow up around them to form a prosenchymatous perithecial wall. The ascogonia give rise to multinucleate ascogenous cells from which croziers and asci form. As the ascocarp develops, an apical meristem produces uninucleate cells that elongate downward into long, slender filaments, the apical paraphyses. From a basal layer of ascogenous cells, asci grow up among the apical paraphyses, which disintegrate as the ascocarp matures. Ascospores are verrucose, with obtuse apiculi. This pattern of development is typical of the Nectria-type of Luttrell.     

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.     

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.     

Use of enlarged cells and nuclei for studying mitosis inNeurospora

Summary Mitotic division stages studied by light microscopy in differentNeurospora crassa cell types clearly resemble prophase, metaphase, anaphase, and telophase stages of higher eukaryotes. 1. When conidia are cultured in liquid medium containing 3.22 M ethylene glycol, they grow without cell division, forming giant spheres with multiple nuclei. In a few giant cells, nuclear numbers remain small (1 to 3) but the nuclei become very large. Seven large chromosomes are seen in some nuclei suggesting polyteny, 14 or more chromosomes are seen in other, very large nuclei, indicating polyploidy. Cell volume and nuclear volume are positively correlated in giant cells. Nuclear divisions are not synchronous within individual multinucleate giant cells. 2. Nuclear division stages were also observed in crosses heterozygous for the dominant mutant banana where haploid prefusion nuclei in late-forming croziers revert to mitosis. Swollen ascogenous hyphae become highly multinucleate after several rounds of mitosis. Mitosis is completely synchronous in nuclei of the same crozier cyst, providing replicate information for unambiguous identification of division stage. 3. Observations are also reported of mitosis in a cell-wall deficient slime strain. Previous observations on mitosis in large nuclei of the ascus are summarized for comparison. The nucleolus persists throughout mitosis in the giant cells, multinucleate reverted croziers, and in the cell-wall deficient slime strain. It is expelled from the dividing nuclei in the ascus. Spindles and spindle pole bodies, which are normally conspicuous in asci, are also seen in normal and reverted croziers, but they have not been clearly identified in the ethylene glycol-induced giant cells.     

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.     

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.     

Morphology,development and cytology of Taphrina maculans Butler

Morphology, development and nuclear behavior of the ascogenous stroma and asci in the infection spots have been described inTaphrina maculans Butler. The fungus forms subcuticular and intercellular mycelium in the leaf tissues and the ascogenous layers originate through division of the subcuticular hyphal cells in the infection sites. Germination of ascogenous cells starts with their elongation in the uppermost layer forming asci and ascospores without formation of stalk cells. Meiosis of the fusion (diploid) nucleus occurs in the young ascus as in otherTaphrina species devoid of stalk cells. The haploid chromosome complement in this species consists of 3 chromosomes (n=3). All the cells in the stromatic layer are potential ascogenous cells and ascus formation continues, until all of them are exhausted in the infection spot. Eight ascospores are normally formed in each ascus, but multi-plication of ascospores may occurin situ later. Three morphologically distinct types of ascus opening are encountered, which are apparently not correlated with prevalent environment. Multiplication of ascospores after their discharge from mature asci occurs by budding proceded by a mitotic division of the spore nucleus. Blastospores (budded cells) germinate into short hyphae and binucleate condition of cells originates by mitotic division of the nucleus. Occurrence of giant cells containing 2 nuclei is often observed. Possible origin of Uredinales fromTaphrina-like ancestors has been indicated due to their close resemblance.     

PERITHECIAL DEVELOPMENT IN HYPOMYCES AURANTIUS

Perithecia of Hypomyces aurantius are initiated by solitary, symmetrical, hyphal coils. During development of the ascocarp, a locule forms concomitantly with centripetal paraphyses, the uppermost of which elongate downward as a palisade of narrow, septate filaments, the apical paraphyses. The initiating coil retains its integrity in the middle of the primordium and becomes the ascogenous system. Uninucleate, diploid cells are part of the ascogenous system. The ascogenous system proliferates through croziers from which asci develop. The haploid chromosome number is 4. The perithecial papillae are formed of spherical cells. This pattern of development is a modification of the Nectria-type of development and characterizes the genus Hypomyces.     

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.     

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.     

STRUCTURE AND DEVELOPMENT OF CLEISTOIODOPHANUS CONGLUTINATUS GEN. & SP. N. (ASCOBOLACEAE)

Cleistoiodophanus represents a new coprophilous genus of the tribe Iodophaneae in the Ascobolaceae (Pezizales). The only species thus far discovered, C. conglutinatus, is described and illustrated. Aspects of its cytological development are described from cultures obtained from apothecia found on sheep dung near Gainesville, Florida. Plasmogamy occurs in acogonial coils, two or three cells of which give rise to ascogenous hyphae. Ascogonia are quickly enclosed by vegetative hyphae and the ascocarp continues in a cleistohymenial development. Unlike Iodophanus and related genera, the excipulum remains intact even after spore maturation and the asci push through the epihymenial regions to release spores. The asci are characteristically thickened at their apices, diffusely amyloid, and somewhat saccate. The asci are predominantly 8-spored, but have been found with four or 16 spores per ascus. A previously undescribed Oedocephalum imperfect stage was induced in culture.     

The Ascogenous Hyphae of Pyronema confluens

The ascogenous hyphae arise from the oogonium, opposite groupsof nuclei, as minute, enucleate papillae. Nuclei pass into themsingly, rarely two at a time, and a knob-like swelling is formed,containing several nuclei and later growing out into one ormore branches. The nuclei are in single file in the branchesand irregularly arranged in the bulbous base. There are frequentlytwo nuclei in a leading position at the tip of the young branch,but the nuclei may become more evenly spaced as the hypha elongates.The nuclei undergo a simultaneous mitosis. The spindles of thedividing nuclei in the branches are not parallel and this is,therefore, not a conjugate division. Walls are formed as ingrowingrings across the spindles so that the ascogenous hypha, whenseptate, has a uninucleate end cell followed by one, or usuallymore, binucleate cells and a basal bulb containing a variablenumber of nuclei. Croziers are formed as lateral, hooked outgrowths from the binucleatecells. After a simultaneous mitosis of the two nuclei a uninucleateend cell, a binucleate penultimate cell, and a uninucleate stalkcell are formed. Thus, the division in the crozier and thatin the ascogenous hypha are alike. The binucleate cell of the crozier may proliferate to form anothercrozier, or it may form an ascus after the fusion of its twonuclei. The stalk and terminal cell of the crozier may anastomoseand grow out to form a lateral crozier. The chromosome number in the mitosis in the ascogenous hyphais twelve and there are twelve bivalents at the first divisionof meiosis in the ascus. The effect of increasing the illumination of the cultures withan electric lamp in addition to diffuse daylight is to ensurethe further development of all early formed sexual organs, tomake the ascogenous hyphae develop rapidly, to make the lattershort and curved in form with few binucleate cells, and to increasethe tendency towards a period of erect proliferation beforethe formation of the asci and lateral proliferation begin. The bearing of the results on current theories of sexualityin the Ascomycetes is discussed.     

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 TRICHOMETASPHAERIA TURCICA

Ascocarps of Trichometasphaeria turcica Luttrell originated in culture as globose parenchymatous stromata within which ascogonia differentiated. As the ascostroma enlarged, stromal cells immediately above the ascogonium produced hyphal outgrowths whose tips grew downward and intertwined beneath the ascogonium. Intercalary growth of these hyphae formed a pseudoparaphysate centrum. Ascogenous hyphae near the base of the centrum produced bitunicate asci which grew upward among the persistent pseudoparaphyses. The ostiole was a broad pore resulting from dissolution of the peripheral stromal cells above the apex of the single locule. Spiny outgrowths from the peripheral cells surrounded the ostiole. The bitunicate asci and ascostromatic ascocarps place this fungus in the subclass Loculoascomycetidae. The pseudoparaphysate centrum and perithecioid ascostroma are characteristic of the Pleosporales. The apparently insignificant character of a protruding conidial hilum was the only essential feature distinguishing Helminthosporium turcicum Pass., the conidial stage of T. turcica, from H. maydis Nisik. & Miyake, a typical representative of species of Helminthosporium with perfect stages in Cochliobolus.     

Orbilia ultrastructure, character evolution and phylogeny of Pezizomycotina

Molecular phylogenetic analyses indicate that the monophyletic classes Orbiliomycetes and Pezizomycetes are among the earliest diverging branches of Pezizomycotina, the largest subphylum of the Ascomycota. Although Orbiliomycetes is resolved as the most basal lineage in some analyses, molecular support for the node resolving the relationships between the two classes is low and topologies are unstable. We provide ultrastructural evidence to inform the placement of Orbiliomycetes by studying an Orbilia, a member of the only order (Orbiliales) of the class. The truncate ascus apex in the Orbilia is thin-walled except at the margin, and an irregular wall rupture of the apex permits ascospore discharge. Ascus, ascogenous and non-ascogenous hyphae were simple septate, with septal pores plugged by unelaborated electron-dense, non-membranous occlusions. Globose Woronin bodies were located on both sides of the septum. Nuclear division was characterized by the retention of an intact nuclear envelope, and a two-layered disk-shaped spindle pole body. The less differentiated nature of the spore discharge apparatus and septal pore organization supports an earliest diverging position of Orbiliomycetes within the subphylum, while the closed nuclear division and disk-shaped spindle pole body are interpreted as ancestral state characters for Ascomycota.     

New fungal genera, Tectonidula gen. nov. for Calosphaeria-like fungi with holoblastic-denticulate conidiogenesis and Natantiella gen. nov. for three species segregated from Ceratostomella

Two morphologically similar groups of ascomycetes with globose to subglobose perithecia, elongate necks, unitunicate asci floating freely at maturity, and hyaline ascospores currently placed in Calosphaeria s. lat. and Ceratostomella s. lat., respectively, are studied. The Calosphaeria-like fungi have groups of perithecia growing between cortex and wood, arranged in circular groups with converging necks and piercing the cortex in a common point; the asci with a shallow apical ring and U- to horseshoe-shaped hyaline ascospores are compared with Calosphaeria pulchella, the type species of the genus. Conidiogenesis of the investigated Calosphaeria-like fungi is holoblastic-denticulate; ramichloridium-like and sporothrix-like conidiophores and conidia were formed in vitro. Ascospore and ascus morphology, structure of the ascal apex, ascogenous system, mode of conidiogenesis and the large subunit rRNA sequences of this group differ considerably from C. pulchella and both groups are unrelated. Thus a new genus, Tectonidula, is described with two accepted species, T. hippocrepida and T. fagi; they are separated by ascospore and ascus morphology and holoblastic-denticulate conidiogenesis from the core species of Calosphaeria. The placement of Tectonidula among perithecial ascomycetes is discussed. The relationship of Tectonidula with Barbatosphaeria and two ramichloridium-like hyphomycetous genera Rhodoveronaea and Myrmecridium is investigated. Three species formerly attributed to Ceratostomella are studied. The revision of the herbarium type specimen and fresh material of Ceratostomella ligneola revealed that it is conspecific with Ceratostomella ampullasca and Ceratostomella similis. The LSU phylogeny clearly separated C. ligneola from Ceratostomella s. str. and morphologically similar Lentomitella. On the basis of molecular sequence data and detailed comparison of morphology of asci, ascospores and ascogenous system the genus Natantiella is described for C. ligneola with C. ampullasca and C. similis as its synonyms. Natantiella produced sterile mycelium in vitro.