Spores and pollen are known from most strata in which macroscopic remains have been found, except for those altered by metamorphism above the rank of zeolite facies.
Some peats have millions of spores and pollen per gram.
Many spores and pollen have distinctive external and internal structural patterns which are characteristic of natural groups of plants, and make possible identification to species, genus, or higher taxonomic unit. A classification based on spore and pollen morphology is also used when the precise natural affinity is unclear. The spore is derived from tundra vegetation which grew at a period when climate was warmer and ice was less extensive. Club mosses were prominent in the polar vegetation of the Early Cretaceous, when New Zealand lay south of the Antarctic Circle. An extinct water-fern which flourished for a short time near the close of the Cretaceous Period.