Glossary of Terms

General Terms

Aperture: A region of the pollen wall that differs significantly from the rest of the wall in its morphology and/or anatomy, and is presumed to function usually as a site of germination.

Helleborus foetidus (illustrating aperture)

Dispersal Unit: Mature pollen is shed in dispersal units. Once shed, the unit either remains permanently united or becomes partly or usually completely disintegrated. If the unit becomes disintegrated, it is usually a monad. If the unit remains united, it is usually a tetrad, polyad, or dyad. Basically, the “dispersal unit” is the body of the pollen grain.
Dyad: A dispersal unit of two pollen grains
Exine: outer layer of the pollen wall
Monad: A pollen grain in the form of a single unit.

Hyacinthoides hispanica–Spanish Bluebell (Monad)

Polyad: A dispersal unit of more than 4 united pollen grains.
Tetrad: A dispersal unit of four united pollen grains.

Gaylussacia brachycera–Box Huckleberry (Tetrad)

Tectum: Outer more or less continuous exine (or outer) layer; tectum condition can be eutectate, semi-tectate, or atectate. Hamamelis vernalis is illustrating a semi-tectate tectum (the gap in the exine layer at the aperture) and Dirca palustris is illustrating a eutectate tectum (no gaps or breaks in the exine layer).

Aperture Type

Colpus: Pollen grain with elongated aperture (length/width ratio > 2) situated at the equatorial region or regularly distributed over the pollen grain.


Helleborus foetidus–Stinking Hellebore (Illustrating colpus apertures)


Compound: Pollen grain with apertures with two or more components (usually colpi with a pore) that are situated in more than one wall layer, can also be called colporus. The “bubbles” on the Amsonia ciliata are the pores.

Amsonia ciliata var. tenuifolia012

Amsonia ciliata–Fringed Bluestar (illustrating compound aperture type)


Inaperturate: Pollen grain without distinct apertures


Hyacinthoides hispanica–Spanish Bluebell (Illustrating an inaperturate pollen grain)

Porate: Pollen grain with a circular or elliptic aperture.


Polonium reptant–Greek Valerian (Illustrating porate aperture type)


Sulcus: Pollen grain with an elongated aperture situated distally.

Convallaria majalis009

Convallaria majalis–Lily of the Valley (illustrating sulcus aperture type)



Echinate: Pollen wall with pointed ornamentation longer and/or wider than 1 um (referred to as echini).


Eutrochium spp.–Joe-Pye Weeds (Illustrating echini)

Granulate: pollen wall with granula, or small granule-shaped bumps. This type of ornamentation is often difficult to see with a scanning electron microscope (SEM), and can become easily confused with perforate ornamentation.

Hyacinthoides hispanica–Spanish Bluebell (Illustrating granulate, potentially perforate ornamentation)

Lophate: Pollen grain with a network-like pattern of ridges (lophae) formed by the outer exine. Similar to reticulate.
[Krigia montana]
Perforate: Pollen wall with holes less than 1 um in diameter. As mentioned above, perforate and granulate can become easily confused with one another when using SEM and are often listed together under ornamentation.
Psilate: Pollen wall with a smooth surface, or a lack of other ornamentation elements. This type of ornamentation can sometimes be difficult to distinguish from granulate or perforate when using SEM.

Gleditsia triacanthos–Honey Locust (Illustrating psilate ornamentation)

Reticulate: Pollen wall with a network pattern formed by exine elements called muri.

Gomphrena spp.–Globe Amaranths (illustrating reticulate ornamentation)

Striate: Pollen wall with elongated exine elements separated by grooves predominately parallel arranged.

Datura metel–Horn of Plenty (illustrating striate)

Definitions adapted from:
 Hesse; Halbritter; Zetter; Weber; Buchner; Frosch-Radivo; Ulrich, Pollen Terminology: An Illustrated Handbook 2009.