The Florissant Fossil Beds National Monument, Colorado, provides a diverse record of megafossil taxa. Some 110-112 species of vascular plants described by Harry D. MacGinitie and studied by Steven Manchester are based on close botanical scrutiny in search of nearest living relatives. A pollen and spore study of the sediments attempted to check modern pollen for affinity with all these identifications on the generic and family level to determine if fossil microspores matching these leaf identifications can be found. Twenty of the 38 families of vascular plants identified from fossil leaves are corroborated by pollen and spores. Of the 84 genera, some 26 have been found in the microfossil record. The 23 genera that microfossil evidence adds to the flora include several new families not previously identified at Florissant: among these are Selaginellaceae, Schizaeaceae, Elaeagnaceae, Rhoipteleaceae, Ericaceae, Onagraceae, Chenopodiaceae, Eucommiaceae. Further, a member of the Fremontodendreae has verified the family Sterculiaceae. Three new conifer taxa of the Pinaceae are added to the flora (Tsuga, an extinct Cedrus type and Pseudotsuga/Larix). A strong bias in favor of wind pollinated plant types is apparent: For example, we can identify affinities with about 3/4 of the wind-pollinated genera with matching pollen or spores, but only 1/3 of the genera that are known to be insect-pollinated types producing low to medium amounts of pollen. The pollen assemblage strengthens the impression that the flora is of warm temperate to sub-tropical in aspect, reminiscent of the summer-moist vegetation of Tamulipas, and Monterrey, in northeastern Mexico.

Key words: Eocene, nearest living relatives, paleoclimate, pollen/spore flora