ISSN:0017-3134    

DOI:10.1080/00173138409428879

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Pollen grains with adhering viscin threads only occur in three unrelated angiosperm families (Onagraceae, Ericaceae, Caesalpiniaceae). Viscin threads consisting of sporopollenin are long, thin, flexible ropes on the pollen surface, and extended between adjoining single pollen grains or pollen tetrads; they should be seen as parts of the exine. The model presented deduces that the manifold viscin thread configurations and sculptures may be attributed to a single, simple exine architecture principle: Distally branched—either smooth or sculptured—columellae form rib-vaultings or arches; if the “ribs” (i.e. the columellar branches) are thick and at some distance from one another, they form muri, as in the Caesalpiniaceae; if the “ribs” are thin and close together, they form a ± compact “tectal network” like in the two other families. Some columellar branches do not contribute to the vaultings, but are enormously elongated, forming simple or (by distortion or by entanglement) complex viscin threads. According to the respective sculpturing of the branches the resulting viscin threads are either smooth or sculptured. Fibres on the pollen surface lacking sporopollenin (and further not derivable from the exine architecture model) should not be termed “viscin threads”.

ISSN:0017-3134    

DOI:10.1080/00173138409428880

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The pollen morphology of 16 out of 350 MexicanQuercusL. species was studied with light and scanning electron microscope. In most species the grains are colporate with distinct ora. Four exine sculpture types are described and their systematic consequences discussed. Moreover, in several cases high standard deviations of the polar axes and equatorial diameters (P, E) show the hybrid nature of specimens which are integrated by the classical definition of the species.

ISSN:0017-3134    

DOI:10.1080/00173138409428881

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

The application of the ion beam etching technique to palynology is described and discussed. Using the technique, structures at different levels in the exine can be exposed for study by scanning electron microscopy. The results obtained vary with the type of pollen and in some cases the grains are unevenly eroded and artifacts produced. In others the tectum may be eroded and the columellae exposed without excessive damage. The results are then comparable to those obtainable at certain levels of focus in light microscopy but with the advantages of higher resolution and the type of image obtained by scanning electron microscopy.

ISSN:0017-3134    

DOI:10.1080/00173138409428882

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Two preparation techniques for light microscopy and five for scanning electron microscopy were compared. The most satisfactory method, both from a quantitative point of view, yielding the least variable results, and from a qualitative one, i.e. without causing any distortion of the pollen grains nor of exine structure and sculpture, was critical point drying with dehydration through acetone. On the other hand, it must be emphasized that the coating and acetolysis of the specimens induced quantitative and qualitative alterations.

ISSN:0017-3134    

DOI:10.1080/00173138409428883

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Pollen grains of three previously described species of Upper Cretaceous dispersed Normapolles from souther Sweden,Extratriporopollenites (Oculopollis) tricepsSkarby,E. (Trudopollis) artifexWeyland & Krieger andE. (Trudopollis) firmusSkarby, and specimens extracted from a single anther (identified asE. artifex), have been analyzed by Fourier analysis. The purpose was to assess quantitatively the diagnostic significance of the outer and inner equatorial contour, and also the validity of the species. Seventy-two radii were measured at equal angular increments along the outer and inner contour, and Fourier series were fitted to the resulting curves. The shapes of the pollen grains may be described by the average radius (zeroth harmonic) and a series of cosine curves relating to their three-fold symmetry (third, sixth, nineth through twenty-fourth harmonic). Multivariate analyses of these harmonics show thatE. firmus, which lacks prominent apertures, stands out as a distinct species. The specimens from the single anther fall within the range ofT. artifex. Some specimens identified asE. tricepsoverlap withT. artifex, indicating that the apertures in this species, described as well-developed, may approach the less prominent apertures ofT. artifex. The results emphasize the difficulties in separating the generaOculopollisandTrudopollisPflug. Typical specimens can be identified, but not intermediate forms. In order to solve this problem a thorough quantitative analysis of dispersed specimens and pollen from anthers is necessary.

ISSN:0017-3134    

DOI:10.1080/00173138409428884

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Elater-bearing spores, once thought to be relatively rare in Upper Carboniferous sediments, are now known to have been produced by many Pennsylvanian sphenophytes. Specimens ofElaterites triferensWilson are radially symmetrical, trilete and possess three circinately-coiled elaters attached to the distal surface by a triangular truss. At the ultrastructural level, the sporoderm consists of two layers: a uniformly thickened exospore, and a thicker, irregularly shaped perispore. The perispore is bilayered with the outer, homogeneous layer forming a series of ridges, and an inner granular layer that is formed by expansion during development. Elaters possess three distinct layers. A comparison of the spores ofElateritesandEquisetumreveals a number of morphological and ultrastructural differences that provide an opportunity to trace the evolution of the sporoderm in these closely related taxa.

ISSN:0017-3134    

DOI:10.1080/00173138409428885

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Experiments comparing volumetric spore collection data averaged into daily, 10-day, or seasonal counts were conducted at various locations within the city of Manhattan, Kansas, USA, and surrounding countryside in 1976–1979. At any given time, differences in number of airspora per m3of air at two or more locations were comparatively great. However, as average numbers were computed for longer periods of time, differences between sites became progressively less. On a daily basis, mean concentrations for the four spore groups during 1976 were significantly different 32% of the possible comparisons between three sites. When 10-day means were compiled for the 100 days sampled at four sites during 1977, significant differences occurred in only 5% of the possible comparisons. For the entire 30 day period of 1976 and 100 day period of 1977, there were no significant differences in mean spore concentrations between any of the sites for any of the four spore groups.

ISSN:0017-3134    

DOI:10.1080/00173138409428886

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

摘要:

Experiments were conducted in 1977 and 1978 on vertical variation of spore concentrations in the atmosphere at 1.5, 9, and 30 m heights with volumetric samplers, which were located at the Rocky Ford Experimental Farm, located 3.2 km north of Manhattan, Kansas city limits (USA). This farm contained turf and grain crop research plots, with general field crops and tallgrass prairie between site and city limits. Spore counts were significantly higher at the 1.5 m height than at either other height when adequate moisture supported local spore production. Spore counts from the 9 and 30 m heights never differed significantly from each other. When moisture was insufficient to sustain spore production locally, all spore forms were uniformly distributed vertically in the atmosphere to the heights studied. In such cases, the major part of the airspora consisted of spores transported in the atmosphere from remote sources.

ISSN:0017-3134    

DOI:10.1080/00173138409428887

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor

ISSN:0017-3134    

DOI:10.1080/00173138409428888

出版商:Taylor & Francis Group    

年代:1984

数据来源: Taylor