bluuebunny/crossref_metadata_2025 huggingface dataset:
Depth of underground plant organs and theoretical survival during fire
Authors: Flinn Marguerite A. , Wein Ross W.
Published: September 2008

For 21 study sites in the Acadia Forest Experiment Station, near Fredericton, New Brunswick, 34 commonly occurring understory species were studied to determine the depth of underground plant organs capable of growing shoots. Depth of these plant parts tended to be species specific. These depth data, together with a knowledge of the sprouting ability of the underground organs, were used to postulate which species would survive fires of varying intensities. Most species found in the litter layer or in the F and H layer of the forested study sites would be susceptible to fires of low intensity. Rubus canadensis, Kalmia angnstifolia, Vaccinium myrtilloides, Pteridium aquilinum, and Viburnum cassinoides would probably survive severe fires because the subterranean plant organs capable of reproduction were found in the mineral soil. In the bog study sites, Vaccinium oxycoccos, Andromeda glaucopliylla, Kalmia angustifolia, Chamaedaphne calyculata, Ledum groenlandicum, and Rhododendron canadense would likely survive severe fires because the plant organs capable of vegetative reproduction were found 25 cm below the surface of the bog.
The generic names Paranectria and Paranectriella and their synonyms
Authors: Hawksworth D. L. , Pirozynski K. A.
Published: September 2008

Paranectriella (P. Henn. ex Sacc.) Höhn. is the correct name for bitunicate ascomycetes segregated from Paranectria Sacc. and must replace the later and not validly published Poeltiella Petrak. A new combination Paranectria oropensis (Ces.) Hawksw. & Piroz. (basionym: Sphaeria oropensis Ces.) is proposed.
Cambial activity and ray cell abundance in Acer saccharum
Authors: Gregory R. A.
Published: September 2008

The ratio of ray and ray cell initials to fusiform initials of the vascular cambium relative to radial growth rate as reflected in the secondary xylem was studied in stems of Acer saccharum Marsh. Ray initials increased in size as they aged, slowly when growth rate was low, rapidly when it was high, but there was little fluctuation in the number of rays per unit of tangential area; as the cambium increased in circumference, the older, larger rays diverged and new small rays arose in intervening areas, thus maintaining a uniform unit area population independent of growth rate. However, since ray size increased rapidly when growth rate was high, the unit area population of ray cells rose abruptly with accelerating growth rate: the relative volume of xylem ray tissue rose from 8.6 to 12.7% of the total xylem volume when annual ring width increased from 1 to 7 mm. When fast growth was not maintained, the unit area population of ray cells declined slowly as the large rays diverged.
Light and electron microscopic investigations in the Dictyonemataceae (Basidiolichens)
Authors: Slocum Robert D. , Floyd Gary L.
Published: September 2008

The nature of the association between the basidiomycetous mycobiont and the blue-green phycobiont in two species of the tropical basidiolichen Dictyonema was investigated using Nomarski light optics and scanning and transmission electron microscopy. Although members of this family may exhibit either a homoiomerous or heteromerous type of thallus organization, the fungus–alga relationship at the cellular level is remarkably consistent. Scytonema filaments are intimately associated with appressorial hyphae of the mycobiont and with extensive intracellular hyphae, which appear to be unrelated to the basidiomycetous fungal symbiont. This is the first report of a lichen displaying an apparent dual fungal symbiosis with the algal host. Association with the intracellular fungus produces no discernible damage to the phycobiont and apparently does not interfere with the symbiosis involving the basidiomycetous fungus.
Notes on Hepaticae collected by John Macoun in southwestern British Columbia
Authors: Godfrey Judith Dean
Published: September 2008

An historically important collection of 330 hepatics collected by John Macoun, the Canadian naturalist–explorer, in southwestern British Columbia has recently been examined and annotated. Since Macoun's specimens have long been cited in the hepaticological literature, a knowledge of the limitations of the data from his identifications and packet labels becomes important. Problems were encountered in regard to species identification, multiple labels on a single packet, multiple collections in a single packet, and incorrect or vague information on habitat and location. A most important single collection of John Macoun, the type specimen of Cololejeunea macounii, is discussed in terms of recent hepaticologial findings in southwestern British Columbia. A list of 73 species identified in Macoun's collection is presented.
Ascocarp development in Lophodermium nitens
Authors: Morgan-Jones J. F. , Hulton R. L.
Published: September 2008

Ascocarps of L. nitens Darker develop in the spring on fallen needles of Pinus strobus L. The ascocarp initial is a compact stroma located between host epidermis and cuticle. Most of this stroma becomes elevated to form the clypeus, while the portion remaining in contact with the epidermis constitutes the incipient hypothecium. As the latter develops, paraphyses originate from the superficial hypothecial cells. Ascogenous elements arise from the bases of certain paraphyses. Occasionally, a paraphysis may give rise directly to an ascus but more frequently to a limited system of ascogenous elements. A number of such systems, similarly produced at various points over the whole hypothecial surface, collectively comprise the hymenium. Any given ascogenous system contains many nuclear pairs. The latter are interpreted as dikaryons because they occur in association with croziers and nuclear quartets, both of which are indicative of conjugate division.
Morphogenetic regulation of seed germination in Orobanche aegyptiaca Pers.
Authors: Kumar Usha
Published: September 2008

The seed of Orobanche aegyptiaca (Orobanchaceae) is very small and contains a subglobose embryo which has not differentiated into radicle, hypocotyl, cotyledons, and plumule. Seeds were aseptically cultured to study germination and the morphogenesis of the embryo. In response to the composition of the medium, the embryo displayed either a monopolar organization or a bipolar organization of the seedling. Medium supplemented either with coconut milk (20% v/v) or yeast extract (5000 ppm) resulted in a monopolar seedling development where the roots and shoot originated from the morphological radicular pole of the embryo. The bipolar pattern of seedling development occurred in response to auxin (0.1 ppm), cytokinin (0.5–10 ppm), gibberellin (1–30 ppm), and strigol (0.01 μg). In bipolar development, the shoot originated from the plumular pole and the roots from the radicular pole of the embryo.
Notes on the size and exine ornamentation of Avena pollen grains
Authors: Gornall R. J.
Published: September 2008

Pollen grain size and exine ornamentation were examined in 13 species of Avena L. (Poaceae), including six A-genome diploids, four tetraploids, and three hexaploids. A cultivated species was represented at each ploidy level. It was found that both pollen size and exine sculpturing patterns showed some correlation with the cytogenetic, morphological, and biochemical evidence which has been used in elucidating the taxonomic relationships within both the A-genome diploids and the hexaploids. However, the pollen data shed less light on relationships within the tetraploids and on relationships between the different ploidy levels. It was observed that the cultivated species at each ploidy level tended to have larger pollen grains and a more complex mode of exine process patterning than their wild relatives. Possible explanations were discussed.
An interrelationship among peroxidase, IAA oxidase, and polyphenol oxidase from peanut cells
Authors: Srivastava O. P. , Huystee R. B. van
Published: September 2008

Two methods were used to separate heme and apoenzyme from the holoenzyme of peroxidase (EC 1.11.1.7) isolated from medium of cultured peanut cells. Apoenzyme prepared by either method lacked peroxidase activity but possessed indole acetic acid (IAA) oxidase and poly phenol oxidase (PPO) (EC 1.14.18.1) activity. When the holoenzyme was reconstituted with heme and apoenzyme, peroxidase activity was restored. The studies on the active site revealed that PPO and IAA oxidase share the same active site on the apoenzyme.
Myricaceae: floral hypothesis for Gale and Comptonia
Authors: Macdonald Alastair D.
Published: September 2008

Organogenesis of the male reproductive structures of Myrica pilulifera, Gale, and Comptonia is compared. In M. pilulifera, which has a compound inflorescence, one to three stamens form in the axils of second-order bracts of the partial inflorescence. In Gale and Comptonia, which do not have compound inflorescences, four stamens arise simultaneously on the flank of the apex of the second-order axis. It is concluded that this defines a floral condition for the family. A model is proposed which explains the probable development of the floral condition from the inflorescence state more adequately than existing floral concepts. Hence, speculation of the phylogenetic status of this family is avoided. Similarly, it is not necessary to debate notions of an angiospermous archetype. Recent knowledge of the family is collated from various disciplines such as taxonomy, anatomy, and palaeobotany to provide a framework for assessing the significance of the discussion of the ‘flower’ vs. ‘inflorescence’ problem.
Sexual reproduction of Abies amabilis
Authors: Owens John N. , Molder Marje
Published: September 2008

Pollen-cone and seed-cone buds which differentiated in the summer and fall of the year before pollination resumed development in early April after about 5 months of dormancy. The sporogenous cells present in the dormant pollen-cone bud divided and formed pollen mother cells which began meiosis by mid-April. Meiosis was completed by late April and mature five-celled pollen was formed by the 3rd week of May. Wind pollination occurred in late May.Each ovule developed a curved funnel-shaped integument tip with a shallowly notched flange-like lip to which pollen readily adhered. No pollination drop was observed. Pollen remained attached to the integument tip but did not germinate for about 1 month, during which time the nucellus grew out nearly to the micropyle and the lip of the integument folded slightly inward bringing the pollen close to the nucellar tip. Pollen tubes then developed rapidly and penetrated the nucellus during the 1st week of July.Each ovule contained a single large megaspore mother cell in the dormant seed-cone bud. Megaspore mother cells underwent meiosis in early May and the single functional megaspore began free nuclear division in mid-May. Female gametophyte development was similar to other members of the Pinaceae and was completed by the end of June. Archegonia varied from two to three and each had two tiers of neck cells.Fertilization occurred in mid-July and early embryo development was rapid. Both simple and cleavage polyembryony occurred and 16-celled proembryos formed. By late July, usually only one club-shaped embryo remained in each ovule. Distinct meristems and cotyledons developed in the embryos in early August and embryos were mature by late August. Ovuliferous scales, usually with two seeds attached, began to be shed in late September. All ovuliferous scales were shed by November.Poor seed production in Abies amabilis (Dougl.) Forbes results partly from the low cone-bearing capacity of the trees, the infrequent occurrence of abundant pollen and seed cones at the high elevation sites, and the high incidence of insect damage to seeds and cones. In addition, A. amabilis and other species of Abies have an unspecialized pollination mechanism, a long period of pollen dormancy after pollination, and a very short time after germination when pollen tubes must develop and penetrate the long nucellar tip. In A. amabilis the archegonia abort very quickly if they are not fertilized. This period when fertilization can effectively occur is very short and remarkably synchronized within a cone and a tree. These, plus the low number of archegonia, may be reasons for the low percentage of viable seed in A. amabilis.
Potential and actual gene exchange among three sympatric species of Vaccinium § Cyanococcus in Highlands County, Florida
Authors: Kloet S. P. Vander
Published: September 2008

Thirty reciprocal crosses among three sympatric species of Vaccinium § Cyanococcus from Highlands County, Florida, show a significant difference in seedling success among the heteroploids V. darrowii (2n = 24) and V. myrsinites (2n = 48) as well as V. fuscatum (2n = 24) and V. myrsinites, but no significant difference in seedling success was observed in crosses between the homoploid taxa V. darrowii and V. fuscatum. The small number of naturally occurring hybrids of these homoploid taxa can be explained by weak incompatibility barriers within the style which result in a consistently longer time for both seed maturation (12% longer) and seed germination (11% longer) in the interspecific cross.
Two new species of Phillipsia from Central America
Authors: Paden J. W.
Published: September 2008

Phillipsia rugospora and P. guatemalensis are described as new species from Costa Rica and Guatemala, Central America. Phillipsia rugospora is distinguished by its yellow hymenium and wrinkled (under the SEM) ascospores. Phillipsia guatemalensis has a rosaceous tan hymenium, relatively thin flesh, and striate ascospores. Both species have been grown in culture. Phillipsia guatemalensis produces holoblastic, hyaline conidia on a low-nitrogen medium. Phillipsia rugospora does not form conidia in culture. However, small, conidium-like structures are produced by germinating ascospores of the latter species.
New evidence of close relationships between Radiigera and Geastrum (Lycoperdales)
Authors: Askew Blain , Miller Jr. Orson K.
Published: September 2008

Specimens of Radiigera fuscogleba Zeller and Geastrum limbatum Fries were studied both in situ and microscopically during their development and are described in detail. They were found to contain identical cell and tissue types, differing only in the manner of dehiscence of the fruiting body at maturity. The same tissue types were observed in five additional species, four in Geastrum and one in Radiigera. The genus Radiigera is transferred to the Geastraceae. New distributional records for the two species of Radiigera and for Geastrum limbatum are reported for the Pacific Northwest along with photographs and illustrations of the microscopic features of both taxa.
Neighbour relationships in grass–legume communities. I. Interspecific contacts in four grassland communities near London, Ontario
Authors: Turkington Roy A. , Cavers Paul B. , Aarssen Lonnie W.
Published: September 2008

A survey of four old grasslands near London, Ontario, showed that different legumes formed consistent relationships with different grass species. Each legume was strongly associated with a particular combination of grass species. It is suggested that each legume–grass combination is selected through the ability of the combination to utilize the soil environment more efficiently than random combinations of species. The ability of species to combine as well as compete is an important factor in maintaining the dynamic stability of grasslands.
Azygosporogenesis in Mucor azygosporus
Authors: O'Donnell K. L. , Ellis J. J. , Hesseltine C. W. , Hooper G. R.
Published: September 2008

Light microscopic and scanning and transmission electron microscopic observations were obtained on azygosporogenesis in Mucor azygosporus Benjamin. Terminal gametangia are delimited by centripetally growing septa but plasmodesmata maintain cytoplasmic continuity between the azygophores and gametangia. Warts develop as regularly spaced patches of electron-opaque wall material on, and ultimately within, the inner primary wall. The mature complex azygosporangium wall is composed of (1) remnants of the membranous outer primary wall, (2) the ornamented layer of electron-opaque, stellate, confluent warts, and (3) a fibrillar, electron-opaque, tertiary layer. A homogeneous, hyaline azygospore wall (quaternary layer or endospore) with stellate warts is laid down within the azygosporangium. A comparison of the fine structural aspects of zygosporogenesis and azygosporogenesis in the Mucorales is presented.
Bud development in Picea glauca. II. Cone differentiation and early development
Authors: Owens John N. , Molder Marje
Published: September 2008

Pollen-cone and seed-cone buds of Picea glauca (Moench) Voss occurred as either terminal or axillary buds. All apices initiated bud scales from late April until mid-July and then differentiated into vegetative, pollen-cone, or seed-cone apices. Potentially pollen-cone apices were usually smaller, had a lower mitotic frequency, and initiated fewer bud scales than potentially vegetative or seed-cone apices. In late July a marked increase in mitotic frequency occurred in differentiating reproductive apices resulting in changes in apical size, shape, and zonation. Leaf, bract, and microsporophyll initiation began at the end of July. All microsporophylls were initiated by early October when pollen-cone buds became dormant. Sporogenous cells had differentiated but meiosis had not begun. Bract initiation began in early August and ovuliferous scale initiation began in late August. Initiation of both stopped in mid-October when seed-cone buds became dormant. Megaspore mother cells were present in dormant seed-cone buds but had not begun meiosis.There was no difference in the time of vegetative, pollen-cone, or seed-cone bud differentiation at the four locations from which collections were made in 1975 and 1976. Differentiation coincided with the end of lateral shoot elongation which was during the last half of July. These results agree with another report from one location in Ontario. Temperature sums also could be an accurate method of determining the time of cone-bud differentiation if calculations were based on the end of vegetative bud dormancy rather than on more arbitrary starting dates. The methods may be applicable to other members of the Pinaceae to determine the optimal time for cone induction treatments.
An addition to the bird's nest fungi of the Hawaiian Islands
Authors: Goos R. D.
Published: September 2008

Collection of Mycocalia reticulata on decaying leaf petioles from the Nuuanu Valley of Oahu is reported and the known distribution of this apparently tropical species is reviewed. The fungus was isolated and fruited on common laboratory media.
Genetic diversity of yellow birch seedlings in Michigan
Authors: Wearstler Jr. Kenneth A. , Barnes Burton V.
Published: September 2008

The objective of the study was to determine genetic differentiation of populations of yellow birch (Betula alleghaniensis Britton) along ecological gradients in Michigan and the Appalachian Mountains. Seeds were collected from populations in each of six physiographic regions of Michigan and in the northern and southern Appalachian Mountains. Seedlings were grown in a common garden in southeastern Michigan. First-year height of progeny, seed weight, initial germination, and germination percentage for 141 yellow birch trees in 30 populations were determined and compared.Significant differences were found among the six Michigan regions for all characters. Strong south–north clinal trends of decreasing height, increasing seed weight, earlier initial germination, and increasing total germination were revealed. Comparisons between physiographic regions showed that tall seedlings were produced by relatively light, late-germinating seeds. Within each region, however, seedlings from earlier germinating seeds tended to exhibit greater height growth. Significant differences were found among populations within a given region for specific characters. In the Appalachian Mountains, southern populations had taller progeny and lighter and poorer germinating seeds than northern populations.Regressions relating each character to 13 site variables were computed. Variation in total height and initial germination were interpreted as the result of differences in the length of the growing season associated with changes in elevation, terrain type, and aspect. Variation in seed weight was associated with differences in the length of growing season and soil moisture regimes.
Mitosis and cell division in Cryptomonas (Cryptophyceae)
Authors: Oakley Berl R. , Bisalputra Thana
Published: September 2008

Mitosis and cytokinesis are examined in Cryptomonas sp., a member of the Cryptophyceae. The beginning of prophase is signalled by the replication of the flagellar bases which are at the anterior of the cell and a proliferation of the microtubules which run from them to the nucleus at the posterior. The microtubules continue to proliferate as the flagellar bases migrate apart and the nucleus migrates to the anterior. They dissociate from the flagellar bases and enter the nucleus as the nuclear envelope breaks down. A rectangular spindle forms and at prometaphase chromatin is scattered along the spindle. From this stage until late telophase microtubules are found attached singly to the chromatin. In metaphase the chromatin forms a solid plate penetrated by tunnels through which microtubules pass and in anaphase the chromatin separates in two masses which move toward the poles as the spindle elongates. In telophase the nuclear envelope re-forms while a number of microtubules remain between the daughter nuclei. The cytokinetic furrow forms during metaphase and constricts gradually until cytokinesis is complete at telophase. A thin ringof amorphous material is seen under the plasma membrane in the cytokinetic furrow. These results suggest that on the basis of mitotic criteria there is little similarity between the cryptophytes and either the dinoflagellates or red algae to which they have been previously linked.
The subcellular organization of stomatal initials in sugarcane leaves: the guard and subsidiary mother cells
Authors: Singh A. P.
Published: September 2008

The subcellular organization of guard and subsidiary mother cells in sugarcane leaves was examined by electron microscopy. Guard and subsidiary mother cells assume a characteristic shape before mitosis and contain variable numbers of mitochondria, proplastids, dictyosomes, and cisternae of rough endoplasmic reticulum. In guard mother cells, the nucleus occupies a central position, whereas in subsidiary mother cells, the nucleus is located toward one end of the cell, near the guard mother cell. Microtubules are found in both guard and subsidiary mother cells and are either closely grouped to form defined preprophase bands or randomly dispersed between the nucleus and the preprophase bands. Many of the dispersed microtubules occur in close association with the nucleus in both guard and subsidiary mother cells. Possible functions for these preprophase microtubules are discussed in relation to their organization in the preprophase band, their orientation, and their distribution within guard and subsidiary mother cells.
Genetics of Gracilaria sp. (Rhodophyceae, Gigartinales). IV. Mitotic recombination and its relationship to mixed phases in the life history
Authors: van der Meer John P. , Todd Edna R.
Published: September 2008

The long-standing problem of mixed phases in life histories of red algae was investigated by genetic techniques. Diploid tetrasporophytes of Gracilaria sp. growing in culture produced functional male and female gametangia in addition to tetraspores. Sporelings resulting from fertilizations involving these gametangia were polyploid, their chromosome numbers indicating that gametes from the tetrasporophyte were diploid. The tetrasporophytes themselves were heterozygous for two genes affecting plant colour. These markers were observed to become homozygous in twin spots of recombinant tissue at the same time that gametangia were formed. All the observations are consistent with the interpretation that both gametangia and recombinant twin spots arise as a consequence of mitotic recombination. The broader implications of these observations for the Rhodophyceae are discussed.
Changes in understory vegetation with increasing stand age in New Brunswick forests: species composition, cover, biomass, and nutrients
Authors: MacLean David A. , Wein Ross W.
Published: September 2008

Understory relationships were examined in 12 jack pine and 11 mixed hardwood stands representing a 7- to 57-year age sequence in New Brunswick. All stands were of fire origin. Percentage cover and frequency of vascular species and major mosses and lichens were presented for each stand. Accumulation of shrub layer and herb layer biomass and distribution of N, P, K, Ca, and Mg were also examined. The biomass showed maximum values in the 10- to 20-year period after fire: it then decreased and stabilized. Contribution of the understory biomass to the total ecosystem biomass ranged from 71–88% on 13-and 16-year-old jack pine stands to 1–6% on the older stands. Nutrient accumulation generally showed a similar pattern to biomass, but some differences occurred owing to variation in nutrient concentration. In particular, shrub layer K increased dramatically on the two oldest jack pine stands; this was postulated to be due to increased dominance of Pteridium aquilinum on these stands. Understory contribution to the total aboveground nutrient pool (tree + understory + forest floor) ranged from 25 to 65% on the younger stands and 5 to 31% on the older stands.
Teliospore germination and basidiospore formation in Gymnosporangium juniperi-virginianae: a regression model of temperature and time effects
Authors: Pearson R. C. , Aldwinckle H. S. , Seem R. C.
Published: September 2008

The influence of temperature on teliospore germination and basidiospore formation in Gymnosporangium juniperi-virginianae was studied in vitro. Teliospores germinated from 8 to 30 °C. Germination was first observed after 2 h from 12–28 °C but longer periods were required at lower temperatures. Promycelia formed basidiospores by 4 h from 12 to 24 °C but not until 7 h at 8 °C. Abortive germination of teliospores, without production of basidiospores, occurred from 26 to 30 °C. No germination was observed from 2 to 6 °C. Multiple regression analyses were performed and an equation relating germination of teliospores to temperature and time was formulated.
Growth of plant cell suspension cultures with ammonium as the sole source of nitrogen
Authors: Martin S. M. , Rose Dyson , Hui Virginia
Published: September 2008

Most media for the culture of plant cells contain two or more sources of nitrogen, and these appear to serve in part to balance changes in pH that occur during the growth cycle in batch cultures. Data presented in the present paper indicate that provision of an external pH control (pH-stat) makes it possible to grow cell lines initiated from Ipomoea purpurea and Glycine max with ammonium as the only nitrogen source. Furthermore, with ammonium hydroxide as the titrant for pH control, the level of ammonium in the medium can be kept at a selected level (combined pH-stat and ammonium-stat) thus providing a greater degree of control over nutrient concentrations during growth than has been possible heretofore.A culture of Ipomoea cells grown under pH-stat – ammonium-stat conditions was comparable in growth rate and other parameters with one grown in a medium containing both ammonium and nitrate without pH control. However, the controlled culture produced more cells per milliliter than the one without control, and these cells remained high in nitrogen (milligram per gram basis) while the nitrogen content of cells in the culture without control declined late in the growthperiod.
Un type complémentaire de profil écologique : le profil écologique 'indicé'
Authors: Gauthier B. , Godron M. , Hiernaux P. , Lepart J.
Published: September 2008

not available
Bryophytes from the area drained by the Peel and Mackenzie rivers, Yukon and Northwest Territories, Canada
Authors: Bird Charles D. , Scotter George W. , Steere William C. , Marsh Alfred H.
Published: September 2008

The distribution and general ecology of 263 bryophyte taxa are presented for an extensive area of coniferous forest, open fens, and alpine terrain along the Mackenzie River in the District of Mackenzie and the Peel River, a major tributary which extends into the Yukon. The continuous or discontinuous permafrost which underlies the area plays a major role in determining the vegetational communities that are present. Fire and disturbance by man initiate succession. Thirty-nine liverworts, 20 peat mosses, and 204 true mosses are reported. There are 43 new reports for the District of Mackenzie and 16 for the Yukon. Cynodontium glaucescens is new to North America. Brachythecium glaciale, B. mildeanum, and B. trachypodium are confirmed for North America. Of the taxa 94.7% are found in Europe and Asia as well as North America, 4.2% are known only from Asia and North America, whereas only 1.1% are restricted to North America. High mountains in the western part of the area, generally nonglaciated during the Wisconsinan, support a flora that contains many Arctic and Arctic–Alpine taxa.
Circaea × intermedia in eastern North America with particular reference to Ontario
Authors: Haber Erich
Published: September 2008

Circaea × intermedia Ehrh. in North America is an interspecific hybrid between C. alpina L. and C. lutetiana L. subsp. canadensis Aschers. & Magnus. In spite of the morphological differences that exist between the European and North American subspecies of C. lutetiana, hybrids from both continents are morphologically identical. Documentation of the intermediacy of the hybrid taxon is presented based on the evaluation of the means of 22 characters of specimens from an Ontario locality at which all three taxa are found.Diploid chromosome counts of 2n = 22 are reported for Ontario populations of the hybrid and parental species. The presence of irregular, somatic chromosome numbers are also reported for all three taxa.Distribution maps for all three taxa in eastern North America are included. In the case of C. lutetiana subsp. canadensis, the northern range is sharply delimited by the Precambrian–Paleozoic bedrock boundary.A table of character comparisons and a key to the three taxa summarizes the salient characteristics of the hybrid and the parental species in eastern North America.
Biology and host range of Haliphthoros milfordensis
Authors: Tharp T. P. , Bland C. E.
Published: September 2008

Light microscope observations were made of the developmental morphology, life cycle, and host range of a strain of Haliphthoros milfordensis Vishniac isolated from the pink shrimp, Penaeus duorarum. Zoospores of the isolate, by virtue of their variation in shape and subapically attached flagella, are not as described previously for this genus. However, they are biflagellate and therefore characteristically oomycetous. Encystment of spores begins with flagellar retraction and rounding-up and terminates with the formation of an external, spined cyst wall. Germination is monopolar, producing germ tubes of various dimensions which fan out into hyphae. Vegetative growth is accompanied by multibranching at right angles and fragmentation. Sporogenesis is holocarpic but unusual in that thallus conversion into spores occurs in delimited segments non-simultaneously and in that spore cleavage is sequential, beginning in the sporangium and ending in the discharge tube. Infectivity tests indicate that H. milfordensis is a facultative parasite occurring on several crustacean hosts: however, the site of infection varies according to host structure.
Transmission and scanning electron microscope observations on the trapping of nematodes by Dactylaria brochopaga
Authors: Dowsett James A. , Reid J. , Caeseele L. Van
Published: September 2008

Constricting ring traps of Dactylaria brochopaga Drechs. were found to be effective trapping agents. Nematodes were held by inflation of the ring cells, inflation resulting from changes in the wall of the luminal face of such cells. The wall structure of the ring cells was found to be more complex than has been previously reported for similar fungi. Membrane-bound, osmiophilic, dense-staining, lysosome-like inclusions were found associated with the trapping surface and appear to play a role in both the trapping and the subsequent penetration process. The ultrastructure of (1) the trapping apparatus before and after its inflation and (2) the nematodes and hyphae during the infection process was studied and is reported herein.
Light microscope observations on the trapping of nematodes by Dactylaria Candida
Authors: Dowsett James A. , Reid J.
Published: September 2008

The host–predator relationship of the myceliophagous nematode Aphelenchus avenue Bastian and the predaceous hyphomycete Dactylaria Candida (Nees) Sacc. was investigated under laboratory conditions, using phase-contrast microscopy of whole-mount preparations and thin resin (Spurr) sections. Adhesive trapping knobs were profusely produced by D. Candida and these proved efficient nematode-trapping agents. Nonconstricting rings were rare and never seen to be operative. Dactylaria Candida was found to be capable of parasitizing nematode eggs.
Sporodiniella umbellata, an entomogenous fungus of the Mucorales from cocoa farms in Ecuador
Authors: Evans Harry C. , Samson Robert A.
Published: September 2008

Sporodiniella umbellata Boedijn, a mucoraceous entomogenous fungus, is redescribed and illustrated. The species is validated by designating a neotype. The fungus was regularly collected on various arthropod hosts in Ecuador, predominantly on insects of the family Membracidae (Homoptera) associated with cocoa farms.
Identification chimique de styryl-pyrones chez quatre hyménochétacées (Champignons, Aphyllophorales)
Authors: Fiasson Jean-Louis , Bernillon Jacques
Published: September 2008

not available
New records and new species of coprophilous Pezizales from Argentina and Venezuela
Authors: Jeng R. S. , Krug J. C.
Published: September 2008

Coprotus baeosporus, Fimaria trochospora, and Iodophanus venezuelensis are described and illustrated. A revised description is provided for Thelebolus caninus n. comb. (= Ascobolus caninus Auersw.). Additional records of many previously recognized Pezizales are reported.
Photosynthesis and photorespiration in submerged aquatic vascular plants
Authors: Lloyd N. D. H. , Canvin D. T. , Bristow J. M.
Published: September 2008

In experiments carried out in a water-vapour-saturated atmosphere, the photosynthesis of submerged leaves of Potamogeton and Myriophyllum was light saturated at a quantum flux of 200 μE m−2 s−1. Saturation of photosynthesis with CO2, however, could not be achieved, even at 3500 μl ℓ−1 CO2. In contrast, floating or aerial leaves of these plants showed saturation with light only at or above a quantum flux of 1200 μE m−2 s−1. In floating leaves of Potamogeton photosynthesis was saturated at 1000 μl ℓ−1 CO2 and in aerial leaves of Myriophyllum saturation was being approached at 2100 μl ℓ−1 CO2.The high resistance of submerged leaves to CO2 transfer makes accurate measurements of photosynthesis and photorespiration difficult. Apparent photosynthesis, though, was stimulated in 2% O2 and inhibited in 50% O2 compared with the rates in air. Oxygen sensitive CO2 evolution into CO2-free air in the light was measured and compensation points of 31 to 75 μl ℓ−1 CO2 were determined. These observations indicate that photorespiration exists in submerged aquatic vascular plants, but the rate of the process cannot be accurately measured.
Photosynthesis and photorespiration in sunflower selections
Authors: Lloyd N. D. H. , Canvin D. T.
Published: September 2008

One hundred and seven sunflower selections were examined by gas-exchange techniques for variations in photorespiration and photosynthesis. Photorespiration was positively correlated(r = 0.73) with true photosynthesis and constituted 14.3% of true photosynthesis or 16.7% of apparent photosynthesis.Selections with differences in compensation point or in the sensitivity of photosynthesis to oxygen or carbon dioxide which would be useful for further studies were not found. Photorespiration would seem to be closely linked to photosynthesis.
Chromosome elimination in a complex hybrid of the genus Hordeum
Authors: Orton Thomas J. , Tai William
Published: September 2008

Hybrid embryos, derived from the cross combining a Hordeum jubatum (4x) – H. compressum (2x) amphiploid and H. vulgare (4x), were observed and found to exhibit instability of chromosome numbers that resulted in an overall loss during the first 8 days of development in embryonic tissues. This instability seemed to be manifest as a progressive increase in the variability of chromosome numbers over this developmental period. The change in the overall mean chromosome number followed no discernible pattern with the exception that counts appeared to be clustered at numbers which are exact multiples of the basic chromosome number (x = 7). For each day postpollination, however, the mean chromosome numbers were significantly lower than the expected zygotic number (with one exception), indicative of net chromosome loss. Based on the data presented and cytological evidence, possible mechanisms are proposed to account for chromosome elimination in hybrid tissues. Chromosome loss may result from an incompatible interaction of the chromosomes and spindle-timing determinants originating from each genome during development or as a consequence of the malfunctioning of a proposed cytoplasmic organelle.
The transition from nonstoried to storied cambium in Fraxinus excelsior. I. The occurrence of radial anticlinal divisions
Authors: Krawczyszyn J.
Published: September 2008

Cell size and arrangement in layers of terminal late xylem parenchyma were interpreted as an historical record of certain types of divisions in the cambium. This allowed study of anticlinal divisions of fusiform initial cells in the cambium of Fraxinus excelsior L. Two types of anticlinal divisions were recognized: oblique (pseudotransverse) and radial (longitudinal). Type designation is, however, arbitrary, since many intermediate configurations between oblique and radial were found. With the exception of radial–lateral divisions, both oblique and radial divisions can be classified as of the left (S) or right (Z) orientational type. The types were nonrandomly distributed. A statistically significant inverse relation was found between the relative length of the anticlinal partition (RLAP) and the length of the dividing cell. Thus, short cells tend to divide radially and longer ones to divide obliquely. As an indirect result, Fraxinus cambium is a mosaic of storied and nonstoried local areas. Consequently, Fraxinus cambium, having an average (but highly variable) RLAP of just over 50%, represents an intermediate between the storied and nonstoried condition.
Spore morphology in the Nidulariaceae (fungi) as revealed by the scanning electron microscope
Authors: Brodie Harold J. , Dietrich H. F.
Published: September 2008

Basidiospores of species representing each of the five genera in the fungus family Nidulariaceae when examined and photographed using the scanning electron microscope appear to have smooth surfaces. Among the species chosen for study, those representing Mycocalia, Nidularia, and Nidula all possess spores which bear a hilum, which has apparently been overlooked in examinations based on light microscopy.
Morphogenesis of protoplasts of Entomophthora egressa in simplified culture media
Authors: Dunphy Gary B. , Nolan Richard A.
Published: September 2008

Protoplasts of Entomophthora egressa MacLeod and Tyrrell were grown in Grace's medium and in two simplified liquid media. These latter media contained reduced numbers of amino acids as compared with Grace's insect tissue culture medium. The pattern of protoplast regeneration was the same in all three media used, but additional stages in the morphogenetic sequence werefound. A spherical mesoprotoplast and an elliptical mesoprotoplast stage with actively moving filopodia were detected early in the growth cycle. The clumping of rod-shaped and spherical hyphal bodies was observed. Mycelial development was very pronounced by 89 h of incubation. The osmolarity and pH of the media were unchanged before this time. The individual hyphae were predominantly initiated by spherical hyphal bodies.All stages of regeneration produced spindle-shaped protoplasts when added to fresh media. The inoculation of spent media with spindle-shaped protoplasts favoured an accelerated morpho-genesis of the cells through the presently reported stages.
Nematophagous fungi: Hohenbuehelia, the perfect state of Nematoctonus
Authors: Barron G. L. , Dierkes Y.
Published: September 2008

A predatory Nematoctonus species (N90) isolated from farmyard soil in Ontario produced gill-forming basidiocarps of Hohenbuehelia on potato dextrose agar. In the presence of nematodes, discharged basidiospores germinated to produce short aerial stalks with terminal adhesive knobs. Germinated basidiospores adhered to the cuticle of nematodes to initiate monokaryotic infection cycles. Multiple basidiospore infections on a single host resulted in dikaryotization in the host body. Crossing single basidiospore cultures demonstrated bipolar sexuality for this species of Hohenbuehelia. The implications of these findings are discussed.
Zoospore ultrastructure of Olpidium cucurbitacearum (Chytridiales)
Authors: Barr D. J. S. , Hadland-Hartmann V. E.
Published: September 2008

Zoospore ultrastructure of Olpidium cucurbitacearum Barr & Dias is described. Isolates from Ontario and Japan are alike. The elliptical zoospore has an anterior nucleus partially surrounded by lobed and branched mitochondria. In the central part an interconnecting network consisting ofsmooth and rough endoplasmic reticulum, a Golgi complex, microbodies, and multivesicular bodies predominates. Vacuoles are abundant in the posterior. Ribosomes occur throughout the cytoplasm. The flagellar apparatus consists of the following: a short fibrillar rhizoplast connecting both kinetosome and nonfunctional centriole to an electron-opaque bar on the nuclear envelope; an elongated transition zone; and a 9 + 2 flagellum axoneme running much of the length of the zoospore through to the posterior end. Props do not connect the kinetosome to the plasmalemma; however, prop parts connect to the kinetosome, and prop parts connect to the plasmalemma at the posterior end of the zoospore. The taxonomic relationship to other chytrids is discussed; the zoospore is similar to that of O. brassicae (Woronin) Dang, and Rhizophlyctis rosea (deBary &Woronin) Fischer, and somewhat similar to that of Rozella allomycis Foust.
Stochastic simulation of patch formation by Hieracium floribundum (Compositae) in abandoned pastureland
Authors: Reader R. J. , Thomas A. G.
Published: September 2008

Plants marked with toothpicks were observed over a period of 2 years to determine recruitment, growth, and death rates for hawkweed patches present in an abandoned pasture in southern Ontario. All rates were affected by patch density, although the effect of density differed for seedlings and rosettes. These field data were used in a mathematical model to simulate the addition of seedlings and rosettes to a newly formed, low-density (160/m2) patch. Simulationresults suggested that it would take at least 25 years for a patch to reach a steady-state density of about 3300 rosettes plus seedlings per square metre.
Preparation, culture, and regeneration of protoplasts from filamentous green algae
Authors: Marchant Harvey J. , Fowke Larry C.
Published: September 2008

High yields of viable protoplasts of the filamentous green algae Mougeotia, Stigeoclonium, Ulothrix, and Klebsormidium can routinely be produced by enzymatic digestion of their cell walls. Regenerating cell walls are detectable by electron microscopy within 16 h of transferring the protoplasts from their isolation medium to growth medium supplemented with an osmoticum. All algae except Ulothrix regenerated filaments that were indistinguishable from untreated material. Stigeoclonium protoplasts, as well as regenerating branched filaments, also gave rise to motile cells and clumps of cells.
Comparative reproductive ability of bigtooth and trembling aspen and their hybrid
Authors: Henry Robert M. , Barnes Burton V.
Published: September 2008

Populus tremuloides and P. grandidentata hybridize readily in southeastern Michigan, and gene flow may be occurring that could alter the parent populations. The purpose of the study was to compare the reproductive capacity and initial growth of hybrids with that of the parent species. Seed-bearing branches of clones of each taxon were collected in nature, and seeds were obtained for growth comparisons. The hybrid clones were lower than the parents in some reproductive traits and intermediate in others. The hybrid exhibited significantly lower seed production per shoot than the parents although some hybrid clones produced more seeds per shoot than certain parental clones. Seed germination percentage of hybrid clones was significantly lower than that of the parents, although individual hybrids had higher germination percentages than some parental clones. Initial height growth of hybrid progeny was somewhat greater at 4 weeks, but was somewhat less than progeny of both parents at 18 weeks. Although the hybrid exhibited some-what reduced fertility, hybrid clones still are capable of producing thousands of germinable seeds which exhibit no deficiencies in establishment or early growth. Thus, no strong barrier was found to prevent the continuous establishment and persistence of backcrosses; gene flow may occur provided suitable disturbed sites are available for colonization.
Zygospores of the Harpellales: an ultrastructural study
Authors: Moss S. T. , Lichtwardt R. W.
Published: September 2008

Structure of zygospores, their zygosporophores, and conjugants in Harpella melusinae, Trichozygospora chironomidarum, Genistellospora homothallica, and Zygopolaris ephemeridarum is described from light and transmission electron microscope studies. Possession of a thickened wall, presence of storage materials, and formation after hyphal conjugation supports the interpretation of these as zygospores. The relationship of the harpellaceous zygospores to those of other members of the Zygomycotina is discussed.
Flux hydriques et métabolisme énergétique dans un peuplement de Lacertidés des îles Kerkennah (Tunisie)
Authors: Vernet Roland , Grenot Claude , Nouira Saïd
Published: September 2008

Water flux and daily energy expenditure were measured with doubly labeled water (3HH18O) in two insectivorous sympatric species of Lacertidae of Kerkennah islands (Tunisia), Eremias olivieri (mean body mass: 1.1 g) and Acanthodactylus pardalis (4.5 g) in a semiarid environment. Water turnover and field metabolic rate of Eremias olivieri (174 μL H2O g−1 d−1 and 250 J g−1 d−1) were, respectively, 2.5 and 5 times higher than those of Acanthodactylus pardalis (70 μL H2O g−1 d−1 and 52 J g−1 d−1). The water turnover of Eremias olivieri is one of the highest known among insectivorous lizards, and the daily energy expenditure of Acanthodactylus pardalis one of the lowest. The most plausible explanations are the differences in the size of the prey eaten by each species at this time of the season and in the duration of daily activity; the daily activity of Acanthodactylus pardalis is short (4.5 h d−1) although it is a sit-and-wait predator, whereas Eremias olivieri is active regularly every day for a longer period (7.5 h d−1) although it is an active forager. The high values of water turnover in Eremias olivieri suggest that food is not the only source of water for lizards in this particular insular environment.