SIZE AND PRODUCTION OF MICROSPORES

The size of the spores and pollen grains found in central Europe ranges from 2 to over 300 micrometers. The stinging nettle (Urtica), for example, produces one of the smallest (and lightest) pollen grains with a diameter of around 10 micrometers while the silver fir (Abies alba) produces one of the largest with a diameter of around 200 micrometers. However, the size of the pollen grains of a species can vary considerably. The different procedures for sample preparation can also effect the diameter of the pollen grains in different ways. Thus, size measurements for the identification of pollen grains should be used with caution.
Pollen- or spore production differs from species to species. In dispersal biology, a distinction is made between plants producing abundant to very abundant wind-dispersed (anemophile or anemogam) pollen and plants producing very little insect-dispersed (entomophile or entomogam) pollen.

Examples of pollen production

very abundant (wind-dispersed)	pine birch (c. 10'000 pollen grains/anther) alder hazel many grasses, e.g. rye	over-represented when compared with the rest of the vegetation.
abundant (wind-dispersed)	spruce fir beech	well represented compared with the rest of the vegetation
little to very little (insect-dispersed)	sycamore (c. 1'000 pollen grains/ anther) ash many forbs, e.g. Lein (c. 100 pollen grains/ anther) or Malve (c. 64 pollen grains/ anther)	Under-represented compared with the rest of the vegetation