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 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.     

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.     

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 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.     

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.     

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.     

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.     

MORPHOLOGICAL STUDIES IN SORDARIA FIMICOLA AND GELASINOSPORA LONGISPORA

Perithecium development in Sordaria, the type genus of the Sordariaceae, is similar to that reported in other genera of this family. Features that characterize the Sordariaceae include the differentiation of the hyphal envelope that surrounds the ascogonium into peripheral wall layers and a pseudoparenchymatous centrum. Broad paraphyses composed of delicate, multinucleate cells arise from the cells of the centrum and completely fill the perithecium, crushing the remaining pseudoparenchymatous cells against the perithecial wall. Sordaria fimicola differs from other species of Sordariaceae studied in the aggregation of the ascogenous cells to form a placenta-like mass in the base of the centrum. Consequently, the asci arise in a cluster rather than in a uniform wall layer. Incomplete observations on Gelasinospora longispora indicate that its development is typically sordariaceous.     

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.     

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.     

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.     

The ultrastructure of septal pores and associated structures in the ascogenous hyphae and asci ofSordaria humana

Summary Septal pores and associated structures have been studied in ascogenous hyphae, croziers and asci ofSordaria humana by means of electron microscopy of serial and random sections. Pores exhibit variable structures from relatively simple pore caps to complex swollen rims with associated membrane cisternae. The simple types are found at the base of the ascogenous hyphae while the complex forms occur at the apex, in the croziers and in very young, presporulation asci. Post-sporulation asci contain a relatively simple type of pore structure. Cells which subtend the ascogenous hyphae exhibit both open and capped pores in their cross walls. Pore structures may be asymmetric in which case they show greater complexity on the side of the cross wall nearest to the apex or crozier. Membranous components of the complex pores are continuous with the endomembrane systems of the two adjacent cells and thus with the outer membranes of the nuclear envelopes. Membrane continuities may connect prefusion nuclei or fusion nuclei in penultimate cells, with nuclei of the stalk and terminal cells of croziers. Some speculation is presented as to the implication and possible roles of these structures in relation to cell differentiation within the ascogenous hyphae and croziers.     

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.     

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 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.     

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.     

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.     

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.     

ASCOCARPIC CENTRUM ONTOGENY OF SPECIES OF HYPODERMATACEAE OF CONIFERS

Studies on the morphology of the ascocarps of 39 species of Hypodermataceae revealed several previously unknown cytological features. Two basic and one intermediate type of centrum ontogeny are discussed. Ascal initiation within Type I centrum occurs in the basal cells of the pseudoparaphyses and involves anastomoses, while ascal initiation within Type II occurs in cells of a plectenchymatous centrum, with no visible anastomosing in the ascocarp. There is frequent anastomosing between vegetative hyphae well in advance of initiation of the ascocarp. Ascal initiation in the intermediate type has ontogenetic sequences similar to those in Types I and II.