Picture of a common bromegrass pollen grain.

The monoporate pollen grain is large and spherical. It is often thin-walled and has a single pore. Monoporate grains are characteristic of grasses, one of the most extensive families of monocotyledonous plants. The grasses include many genera ranging from wheat and other cereal grains to sugar cane and bamboo. Monoporate grains are found in the fossil record beginning from the Cretaceous but are generally not common before the Oligocene epoch of the mid Tertiary.