Edward L. Vezey

Hexamethyldisilazane as a Drying Agent for Pollen Scanning Electron Microscopy

Use of hexamethyldisilazane (HMDS) as a final dehydrating solution provides robust, undistorted secondary electron images of a variety of angiosperm and gymnosperm pollen grains, including those considered to be susceptible to collapse in the scanning electron microscope. Ease of handling, low cost, lack of specialized equipment, minimal expenditure of time, and high rate of success are factors that favor HMDS over other drying agents for preparing pollen grains for scanning electron microscopy.

The Use of Osmium-Thiocarbohydrazide for Structural Stabilization and Enhancement of Secondary Electron Images in Scanning Electron Microscopy of Pollen

Abstract Pollen grains stained in a sequence of osmium (O) and thiocarbohydrazide (T) solutions (collectively known as OTOTO) appear structurally stable and undistorted in the scanning electron microscope (SEM), and usually do not require special drying. In fact, OTOTO can be regarded as another special drying method in palynology. This sequential incubation also strikingly increases the electrical conductivity of pollen grains in the SEM. Compared to standard sputter-coating or vacuum evaporative procedures, OTOTO reduces charging and yields secondary electron images with significantly higher resolution.

Computerized feature analysis of exine sculpture patterns

Abstract This study introduces computerized feature analysis of SEM micrographs of pollen exines to quantify sculpture patterns with tectal perforations of any size. The usefulness of measurements generated was tested in a variety of systematic applications. First, sculpture variation between similar exines of two Anisophylleaceae species was quantified. This analysis also demonstrated the need to modify the term scrobiculate to describe patters intermediate between the morphological categories punctate and microreticulate. Second, data from three Capparaceae species were used in a principal components analysis, permitting study of morphological variation within and among species. Finally, morphometric data used in the principal components analysis were converted to discrete character states using gap-coding. The resulting characters were then employed in a cladistic framework to study exine character evolution in a quantitative manner.

A numerical approach to pollen sculpture terminology

We present a key synthesizing pollen-sculpture terminology for grains having perforations or lumina of any size and spatial distribution. The key uses quantitative criteria to distinguish five non-overlapping qualitative terms (reticulate, microreticulate, foveolate, scrobiculate, and punctate). In addition, the range of quantitative variation encompassed by these qualitative terms is highlighted, including ways to express and compare that variation using computerized image analysis of SEM micrographs. Finally, a mathematical analysis combined with image-analysis measurements is used to explore the relationships between the terms outlined above and two closely related terms, tectate and semitectate.

ANALYSIS OF THE THANIKAIMONI PALYNOLOGICAL INDICES

Summary The series of five bibliographic indices for extant pollen compiled under the editorship of the late G. Thanikaimoni are analyzed with respect to instrumentation used in characterization of the angiosperm pollen wall. It is clear that scanning electron microscopy has become the most common means for examining pollen and that while the number of publications involving pollen morphology increases yearly, only a small number of genera have been studied with either scanning or transmission electron microscopes.

Computer-generated key to pollen of tribe Swartzieae (Leguminosae)

Abstract A key to 27 pollen types from tribe Swartzieae (Leguminosae) was created using the DELTA (DEscription Language for TAxonomy) computer system and published data from light (LM), scanning electron (SEM) and transmission electron (TEM) microscopic studies. DELTA was also used to produce natural-language descriptions of all pollen types, permitting a tentative identification to be checked against all characters in the database. Features of DELTA used to construct the key and natural-language descriptions are described in detail.

Searching for a foveolate pollen exine

Abstract Ninety-five scanning electron micrographs of pollen exines with perforations, lumina, pits, or depressions were photocopied from the palynological literature, examined by computerized image analysis, and categorized using existing numerical definitions for reticulate, microreticulate, scrobiculate, punctate and foveolate. For comparison, we also recorded descriptive terms used for these pollen surfaces in the original literature source. Most exines examine were reticulate or scrobiculate. Only two were punctate, an anomally we atrributed to sampling bias. No exines were foveolate. We concluded that pollen exines with foveolate surfaces are very rare or non-existent. We also demonstrated that many overlapping sculpture terms are used to describe very similar exines, a situation that may adversely affect the usefulness of palymological information in larger systematic data sets.

Systematics of the genus Striatocorpus (Krutsch 1970) Farabee et al. 1991

Abstract Recent morphological analysis of Triprojectacites indicates the need to elevate the subgenus Striatocorpus Krutzsch to the generic level. The combination of parallel striae and an angled (V‐shaped in equatorial view) “heteropolar”; body are unique to Striatocorpus among all Triprojectacites thus far examined. The known stratigraphic range of Striatocorpus is from upper Campanian to middle Maastrichtian in the western United States, Canada, Siberia, and northern China. Species included are Striatocorpus kurtos (Zhou & Wang) comb. nov., S. pyriformis (Norton) Farabee, and S. striatus (Funkhouser) comb. nov. We propose that Striatocorpus evolved from parallel‐striate, non‐angled‐body, long‐colpate pollen similar to Translucentipollis plicatillis Chlonova. Alternate hypotheses are also discussed and evaluated.

Statistical analysis of computer-generated measurements from manually outlined pollen perforations

Abstract Quantitative pollen-sculpture variation can provide systematically useful information. To test manual-outlining techniques used with automated measurement of pollen-sculpture features, we conducted several experiments in which perforations were traced with felt-tip pen onto thin sheets of plastic. In each experiment, seven individuals made five tracings of the same pattern. Tracings were then digitized and perforations measured using image-analysis software. Three test patterns were used: (1) an SEM micrograph with “real” pollen perforations; (2) a computer-generated test pattern that simulated very small pollen perforations; and (3) a computer-generated test pattern that simulated very large pollen perforations. Experiments examined the effect on precision and accuracy of using: (1) opaque-black versus transparent-red ink; (2) small versus large perforations; and (3) fuzzy- versus sharp-edged perforations. Tracings were statistically compared using the coefficient of variation and an analysis of...

Silver berm containment of pollen for observation with scanning electron microscopy

Abstract The application of silver paint on specimen mounts to form berms is helpful in localizing pollen for examination with scanning electron microscopy. This is especially useful with rectangular boats because pollen located on the boundaries is out of the field of view when examined at high magnifications. Silver berms are not an impediment to photography and pollen grains lying on them are often better grounded, thus enhancing the final image. Distracting silver backgrounds can be “painted out” of the prints if desired. Berms can also be used effectively on circular specimen mounts, particularly when small quantities of rare pollen or even an isolated fossil pollen grain needs to be centered for high resolution study.