Pollens are propagules from vascular plants and spores are the propagules from the nonvascular plants. Spores have a shell (exine)
consisting of one layer generally though a loose outer sack, the perine, may be present (see fern spores for an example). Pollens have an exine typically of two or more layers. Spores are not optically active, that is
when they are viewed between crossed polarizing filters they disappear. Pollens are often optically active or contain
starch grains that are optically active. These pollens are visible when viewed between crossed polarizing filters. As
pollen grains age they loose the optical activity and the starch grains dissipate into the environment. These starch grains
carry the allergen for that pollen with them. Most standard guides to pollen identification are based on "acetolyzed" grains,
chemicaly processed pollen that removes the contents of the grain and most of the optical activity of the grain. It also
swells the grain. This is a necessary practice in the analysis of fossil grains but for environmental analysis the fresh
pollen grain is more characteristic. Most of the pollen grains shown here are fresh. They are from honeybee frass (fecal
pellet), regional honey samples, or from recent environmental samples. An abridged morphological key is provided here (see
References at end). - Click here
to link to a good website containing a glossary of morphlogical terms used to describe pollens and spores.
