Trees and shrubs with oval (2-5 cm) toothed leaves, generally rough
bark. Reproduction by woody female and male catkins, seeds winged 2 mm.
Temperate to alpine, Northern Hemisphere. Many species are riparian,
others are understory species.
Pollen light micrograph:
Pollen oblate, 20 - 30 µ.m., stephanoporate (4 - 5 pores in equatorial plane) with
distinctive lines of thickening (arci) joining the pores in
both hemispheres. Surface scabrate to rugulate. Arci are
external and internal.
Pollen scanning electron micrograph (SEM)
Arci are not evident on the grain shown above, but
are evident in the sem by
Martin and Drew.
Production and Dispersal:
Alders are wind pollinated, so production and dispersal
are very good. Alder pollen is common. In the Pacific Northwest,
alder is common in canopy openings of the coniferous forest, and
was abundant during the mid-Holocene when the forest became open.