OTHER RELATED TECHNIQUES
While this paper represents the first mention of the use of such software for paleopalynology, other superior imaging techniques do exist. The most familiar is of course the scanning electron microscope (SEM), which uses a focused beam of electrons for analyzing the specimen. The possibility of magnification with larger depth of field makes it a very desirable and useful tool for palynology (Ferguson et al. 2007). While it is evident that electron microscopy is an important tool for palynological morphological analysis, its use is limited by a number of factors. The preparation techniques for the samples differ completely from those routinely used for optical microscopy. Pollen grains must be mounted on a metallic stub and metallized by ion sputtering prior to observation. This implies that samples previously mounted in a permanent medium on a microscope slide cannot be analyzed under SEM.
Another lesser known tool is the confocal laser scanning microscope (CLSM). This microscopical technique, derived from optical microscopy, allows for the imaging of very thin optical sections (at a micrometer scale) (Cogswell and Sheppard 1992;
Sheppard and Shotton 1997;
Claxton et al. 2005). These optical sections are not only very thin, but also do not present any out of focus zone corresponding to the parts of the object above and below the focus plane. Computer reconstruction from these thin sections allows for very precise three- dimensional reconstruction that can be viewed from different angles. This approach is valuable as it represents a non-invasive way of re-imaging and re-investigating type collections. Use of CLSM for paleopalynology on the
Duxbury (1983) Albian dinoflagellate cysts collection was part of a project undertaken by the Natural History Museum of London (Feist-Burkhardt et al 1998;
Feist-Burkhardt and Pross 1998).
However, both electron microscopy and confocal laser microscopy require the use of expensive heavy items of equipment, which may not be routinely available in any palynological laboratory. In contrast, optical microscopes are part of the standard equipment, and optical photomicrographs are still the standard for comparison. CombineZM, and similar software, can be routinely used as a convenient way to depict palynomorphs in publications, but they do not pretend to replace more advanced imaging methods.