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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Plant systematics and evolution 154 (1986), S. 31-39 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Lactoridaceae ; Ultrastructure ; pollen ; fossil pollen (Cretaceous)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The pollen wall ultrastructure of the primitive AngiospermLactoris fernandeziana Phil. (Lactoridaceae) is described. The monosulcate aperture, granular wall structure and sacci (all primitive features) suggest placement of this family in theMagnoliales. Pollen ofLactoris is compared to fossil dispersed pollen from the Lower and lower-Upper Cretaceous. The fossil pollen shares characteristics which are restricted to theLactoridaceae suggesting that this family was present during the early Cretaceous.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1615-6110
    Keywords: Pteridophyta ; Filicopsida ; Lophosoria ; Cyatheacidites ; Palynology ; sporoderm ultrastructure ; Cretaceous ; Tertiary
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The distinctive spores produced byLophosoria, an extant monotypic fern, are examined ultrastructurally and correlated with the sporoderm of fossilCyatheacidites. The morphological and ultrastructural similarity of the two taxa provide additional information that can be used to trace the evolutionary history of this spore type.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 325 (1987), S. 10-10 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR-The statements made by Francis Auburn in his recent review of two books about Antarctic (Nature 323, 22; 1986) were disconcerting to us as Antarctic scientists. We do not, of course, represent the official US government stance on the continent, but as scientists who are involved in research ...
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 17 (1978), S. 145-157 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have measured the ultraviolet CD spectra for covalently closed and linear forms of phage PM2 DNA in solution. We find that increased concentrations of salt or ethanol (up to 50% ethanol by weight) depress the long-wavelength positive CD bands in the spectra of both forms of DNA, although the spectrum of the native covalently closed DNA always has a slightly larger magnitude of these bands than does the spectrum of the linear DNA. In addition, both DNAs are equally capable of undergoing a transition to the A conformation in 70-80% ethanol at low Na+ concentrations. Thus, the constraint imposed by the covalent closure of a DNA molecule does not seem to hinder its conformational response to these changing solution conditions. Lang [(1973) J. Mol. Biol. 78, 247-254] has found by electron microscopy that T7 DNA has an inherent ability to condense into compact particles, suggested to be supercoils of multiple order. Both covalently closed and linear forms of PM2 DNA also become condensed when the DNA, in 0.2M ammonium acetate and 1 mM EDTA, is exposed to ethanol and subsequent drying on specimen grids [Lang, D., Taylor, T. N., Dobyan, D. C. & Gray, D. M. (1976) J. Mol. Biol. 106, 97-107]. Under similar conditions, in solutions of 0.2M ammonium acetate and 1 mM EDTA to which ethanol is added, we have measured the CD spectra of both covalently closed and linear forms of DNA. Below ethanol concentrations at which the DNA obviously precipitates, the CD spectra of both forms have reduced long-wavelength positive CD bands.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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