Problematical taxonomic criteria in the Chytridiales: comparative morphology of 10 Entophlyctis sp. isolates

1971 ◽  
Vol 49 (6) ◽  
pp. 977-987 ◽  
Author(s):  
Tom Booth
Keyword(s):  
Synthetic Medium ◽  
Pollen Grains ◽  
Comparative Morphology ◽  
Western Canada ◽  
Review Of The Literature ◽  
Single Spore ◽  
Exact Identification ◽  
Established Species ◽  
Size And Structure

The criteria generally used in distinguishing taxa among the Chytridiales are size and structure of the zoospores, sporangium wall ornamentations, discharge papillae and tubes, presence or absence and structure of apophyses, nature and structure of rhizoids and number and position of rhizoidal axes, thallus development and relation to the substratum, monocentricity or polycentricity, and operculation. A review of the literature, however, reveals that these criteria are not sharply defined but highly variable and unstable for purposes of exact identification. This variability has become evident from a study of 10 single spore isolates of an Entophlyctis species collected in western Canada and the U.S.A. and grown on pollen grains and a synthetic medium. A comparison of the variations common to all isolates relates this species to several different established species of the genus which grade into one another and result in only three valid taxa, E. apiculata, E. crenata, and E. reticulospora. Also, the variations of the isolates relate this Entophlyctis sp. to different genera, subfamilies, families, and series, and make various current taxonomic dispositions and concepts of little value.

NOTES ON THE CANADIAN TUCKAHOE, ITS OCCURRENCE IN CANADA AND THE INTERFERTILITY OF ITS PERFECT STAGE, POLYPORUS TUBERASTER JACQ. EX FRIES

1951 ◽  
Vol 29 (2) ◽  
pp. 147-157 ◽  
Author(s):  
T. C. Vanterpool ◽  
Ruth Macrae
Keyword(s):  
Populus Tremuloides ◽  
Western Canada ◽  
Single Spore ◽  
Canadian Prairies ◽  
Perfect Stage

The Canadian tuckahoe is the perennial sclerotium of Polyporus tuberaster jacq. ex Fries. It is commonly found in the parkland belt of the Canadian prairies where land supporting, virgin poplar groves, mainly Populus tremuloides Michx., is being brought under cultivation. Sporophore as many as three to a single sclerotium, appear in late June and July. Interfertility studies with single spore cultures isolated from sporophores derived from four sources in Western Canada and from one source in Italy have shown that both the Canadian fungus and the European P. tuberaster are heterothallic, have the tetrapolar type of interfertility, and are interfertile.

Pollen morphology of the Rosaceae of western Canada. IV. Luetkea, Oemleria, Physocarpus, Prunus

1991 ◽  
Vol 69 (12) ◽  
pp. 2583-2596 ◽  
Author(s):  
R. J. Hebda ◽  
C. C. Chinnappa ◽  
B. M. Smith
Keyword(s):  
Pollen Morphology ◽  
Pollen Grains ◽  
Pollen Grain ◽  
Western Canada ◽  
Prunus Virginiana ◽  
Prunus Spinosa ◽  
Pore Area ◽  
Pollen Grain Size ◽  
Triple Points ◽  
Scanning Electron

Pollen grains of 12 species of western Canadian rosaceous genera, Luetkea, Oemleria, Physocarpus, and Prunus, were studied in the light microscope and scanning electron microscope. All pollen grains are produced as isopolar, radially symmetrical, usually tricolporate monads. Grains are predominantly spheroidal with a circular to triangular amb. Most of the species exhibit a well-developed chambered aperture complex at the equator, formed by a pair of sexinal flaps whereas in Prunus spinosa, Prunus americana, and Prunus virginiana the chamber is absent or weakly developed. Oemleria cerasiformis has no pore flaps. Apertures of Prunus emarginata and Prunus virginiana often have an equatorial bridge over the aperture complex. The exine of Prunus, Physocarpus, and Luetkea pollen is tectate perforate, like that of many Rosaceae. Sculpturing consists of ridges and valleys that form a striate to rugulate pattern. Ridges and valleys tend to be mainly parallel to the colpus but often loop near the poles. Pollen grains of Prunus spinosa are always rugulate or vermiculate with ridges arranged randomly. Oemleria cerasiformis pollen appears tectate imperforate. Ridges and valleys intersect at triple points in the subpolar region and curve in a semicircle around the pore area. On this basis Oemleria pollen is distinct from all other western Canadian Rosaceae. Pollen grain size ranges from small for Luetkea pectinata (17 μm in diameter) to medium for Prunus spinosa (36 × 33 μm). Key words: pollen morphology, Rosaceae, Western Canada, systematics.

Intracerebral myiasis from Hypoderma bovis larva in a child

1989 ◽  
Vol 71 (6) ◽  
pp. 929-931 ◽  
Author(s):  
Müfit Kalelioğlu ◽  
Gönül Aktürk ◽  
Fadiil Aktürk ◽  
Sezer Ş. Komsuoğlu ◽  
Kayhan Kuzeyü ◽  
...  
Keyword(s):  
Computerized Tomography ◽  
Ct Scans ◽  
Intracerebral Hematoma ◽  
Review Of The Literature ◽  
Content Type ◽  
First Case ◽  
Hypoderma Bovis ◽  
History Of ◽  
Exact Identification ◽  
Fine Print

✓ Cerebral myiasis with a 10-day history of convulsions due to an intracerebral hematoma caused by a Hypoderma bovis larva is reported in an 8-year-old child. Computerized tomography (CT) showed the hematoma in a right parieto-occipital location. The H. bovis larva and the extensive intracerebral hematoma were discovered during surgery. Among human parasitoses, cerebral myiasis is rare: a review of the literature revealed only two reports, one published in 1969 and one in 1980. This is the first case that has been diagnosed as cerebral myiasis with exact identification of the Hypoderma bovis larva both from the CT scans and at surgery in a patient during life.

Pollen morphology of the Rosaceae of western Canada. II. Dryas, Fragaria, Holodiscus

1988 ◽  
Vol 66 (4) ◽  
pp. 595-612 ◽  
Author(s):  
R. J. Hebda ◽  
C. C. Chinnappa ◽  
B. M. Smith
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Pollen Morphology ◽  
Silicone Oil ◽  
Pollen Grains ◽  
Western Canada ◽  
Dryas Octopetala ◽  
Fragaria Virginiana ◽  
Fragaria Species ◽  
Scanning Electron

Morphology and geographic variation of pollen grains of three genera of the Rosaceae (Dryas, Fragaria, Holodiscus) of western Canada were studied using the light microscope and scanning electron microscope. Dryas spp. pollen is tricolporate with a weakly developed fusiform aperture in the colpus, which upon expansion of the grain becomes a large rectangular opening. Sculpturing consists of ridges and valleys (striate or rugulate), the latter containing perforations, which grades to a network of ridges and perforations (reticulate) at colpus margins. Ridges are parallel to the colpus or form looping patterns. Dryas integrifolia and Dryas octopetala pollen in silicone oil usually are larger than those of Dryas drummondii. Fragaria spp. pollen is tricolporate with a well-developed complex equatorial aperture. Fragaria chiloensis and F. vesca exhibit a lobed and equatorially extended endoaperture, which is overarched by sexine. Fragaria virginiana usually has a less distinct endoaperture. Fragaria species have a fusiform colpus operculum. Sculpturing consists of nonasastomosing ridges parallel to the colpus and valleys containing obscure microperforations. Holodiscus discolor pollen is tricolporate. Sculpturing is striate to reticulostriate, consisting of ridges and valleys with perforations. A distinct zone, either lacking ridges or of densely packed ridges, borders the colpus.

scholarly journals Inhibition of cytokinesis in the microspores of Tradescantia bracteata Small, by caffeine

2015 ◽  
Vol 45 (4) ◽  
pp. 469-476
Author(s):  
M. Charzyńska ◽  
I. Pannenko
Keyword(s):  
Cell Wall ◽  
Nutrient Medium ◽  
Pollen Grains ◽  
Necessary Condition ◽  
Similar Shape ◽  
A Cell ◽  
Size And Structure

In isolated stamens of <i>Tradescantia bracteata</i> planted in nutrient medium cytokinesis in microspores was inhibited by caffeine and binucleate pollen grains were formed. Both the nuclei were of similar shape, size and structure and did not undergo further changes. It seems that separation of the polarly differentiated microspore protoplast by a cell wall is a necessary condition for differentiation of the gametophyte nuclei to generative and vegetative.

scholarly journals Silicone Oil as a Mounting Medium for Pollen Grains

1960 ◽  
Vol 4 (1) ◽  
pp. 1-24
Author(s):  
Svend Th. Andersen
Keyword(s):  
Pollen Analysis ◽  
Silicone Oil ◽  
Pollen Grains ◽  
Comparative Morphology ◽  
Media Influence ◽  
Chemical Treatments ◽  
Embedding Medium

With the refinement of pollen analysis and with the need for more exact identifications, a number of special problems present themselves. Detailed comparative morphology becomes increasingly important and with it the requirements as to the properties of the embedding medium increase.The problems of species identifications, especially, call for a comparison of the "coarseness" of morphological details. Hence it becomes desirable that the pollen exines to be studied are found in comparable states of expansion. Chemical treatments of various kinds are well known to modify the size of pollen grains greatly, but as will be shown below the qualities of the embedding media influence their immediate state too.

Pollen morphology of the Rosaceae of western Canada. III. Geum

1990 ◽  
Vol 68 (6) ◽  
pp. 1369-1378 ◽  
Author(s):  
R. J. Hebda ◽  
C. C. Chinnappa
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Light Microscope ◽  
Pollen Morphology ◽  
Pollen Grains ◽  
Western Canada ◽  
Polar Diameter ◽  
Scanning Electron

Pollen grains of eight species of Geum (Rosaceae) from western Canada were studied in the light microscope and the scanning electron microscope. The taxa included Geum aleppicum, Geum calthifolium, Geum glaciale, Geum macrophyllum, Geum rivale, Geum rossii, Geum schofieldii, and Geum triflorum. All taxa produce pollen grains in monads that are isopolar, radially symmetrical, and predominantly tricolporate. Tetracolporate grains occur especially in Geum rossii and Geum calthifolium. Grains are subspheroidal to subprolate with a circular to subtriangular amb. All taxa exhibit a well-developed chambered aperture formed by overarching pore flaps. Flaps extend over the aperture but do not join to form an equatorial bridge. The chamber of Geum schofieldii is distinct and complex, often extending equatorially along a sinuous path to the adjacent aperture. Exine is tectate, microperforate, with a thin nexine. Sculpturing is striate or occasionally rugulate and consists of ridges and valleys with microperforations on valley floors. Ridges and valleys are oriented predominantly parallel to the colpus but occasionally curve or loop near the poles. Sculpturing of Geum schofieldii pollen, is predominantly striate but exhibits a unique verrucate to rugulate pattern along the equator caused by elaboration of the sexine. Polar diameter varies from ca. 20 μm in Geum macrophyllum to 33 μm in Geum schofieldii. The distinctness of Geum schofieldii pollen supports specific status.

scholarly journals A Preliminary Study of the Chemical Nature of the Toxic Substances produced by the Salmonella Group of Organisms

1927 ◽  
Vol 27 (1) ◽  
pp. 44-48 ◽  
Author(s):  
E. E. Ecker ◽  
C. Rimington
Keyword(s):  
Intravenous Injection ◽  
Chemical Nature ◽  
Synthetic Medium ◽  
Broth Culture ◽  
Similar Reaction ◽  
Toxic Substances ◽  
Review Of The Literature ◽  
Preliminary Study

The production of soluble toxic substances in broth cultures of these bacteria is well known. Berkefeld nitrates of such cultures are usually toxic for the rabbit upon intravenous injection. A review of the literature has been given by Ecker (1917, 1925) and by Branham (1925). Subsequent studies of these workers have shown that Berkefeld filtrates of synthetic medium (Braun and Cahn-Bonner, 1921) cultures yielded toxic substances inducing a similar reaction in the rabbit. Little is known concerning the nature of these substances beyond that they are relatively thermostabile; on dialysis of the broth culture nitrate the toxin is withheld within the collodium sac.

scholarly journals Retribución y composición del Consejo de Administración : evidencia empírica para las empresas cotizadas españolas

2009 ◽  
pp. 203 ◽  
Author(s):  
Elena Merino Madrid ◽  
Montserrat Manzaneque Lizano ◽  
Regino Banegas Ochovo
Keyword(s):  
Board Of Directors ◽  
Stock Exchange ◽  
Agency Problems ◽  
Chief Executive ◽  
Administrative Staff ◽  
Review Of The Literature ◽  
Composition And Structure ◽  
The Board Of Directors ◽  
The Empirical Analysis ◽  
Size And Structure

Este trabajo tiene como objetivo principal analizar las características de las empresas españolas cotizadas en el Mercado Continuo durante el ejercicio 2007, excluyendo las empresas financieras, en relación a la retribución, composición y estructura del Consejo de Administración, a fin de observar si éstas reúnen ciertas condiciones que inhiban o aviven los problemas de agencia entre accionistas y directivos. Para ello, en primer lugar, se ofrece una revisión de la literatura previa que versa sobre el conflicto de intereses entre propietarios y directivos en relación a la compensación y composición de los órganos de administración; en segundo lugar, se describe la metodología utilizada para el desarrollo del análisis empírico y se presentan los resultados del mismo; y, por último, se exponen las principales conclusiones.De tos resultado obtenidos se deduce que algunas de los aspectos de las empresas cotizadas españolas pueden redundar en la aparición de problemas de agencia entre directivos y accionistas, entre ellos: la dimensión y estructura de los sistemas retributivos, la falta de transparencia informativa al respecto de las retribuciones individuales de consejeros y la acumulación de poderes del presidente del Consejo de Administración y el primer ejecutivo.<br /><br />This paper mainly aims at analysing the characteristics of Spanish companies listed in the Stock Exchange during the year 2007, financial companies excluded, in relation to the remuneration, composition and structure of the Board of Directors, in order to see if the companies meet certain conditions that inhibit or intensify the agency problems among shareholders and managers. In order to do this, firstly, we provide a review of the literature which deals with the conflict of interests among owners and managers in relation to the composition and compensation of the administrative staff; secondly, we describe the methodology used to develop the empirical analysis and present the results of it. Finally, we discuss the main conclusions.From the results obtained we conclude that some of the characteristics of Spanish listed companies may produce agency problems among managers and shareholders, including the size and structure of the remuneration scheme, lack of transparency regarding individual remuneration of directors and the accumulation of power when the president of the Board of Directors and the chief executive officer are the same person.

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