Members of the Gentian Family with Floral Parts in 4s:
Columbia Frasera, Whitestem Frasera, White-stemmed Frasera: Swertia albicaulis (Synonyms: Frasera albicaulis ssp. columbiana, Swertia columbiana)
Desert Centaury, Tall Centaury, Western Centaury: Zeltnera exaltata (Synonym: Centaurium exaltatum) - Corolla lobes number 4 or 5.
Members of the Gentian Family with Floral Parts in 5s:
Common Centaury, European Centaury: Centaurium erythraea
Explorer's Gentian, Mountain Bog Gentian, Rainier Pleated Gentian: Gentiana calycosa (Synonyms: Gentiana calycosa ssp. calycosa, Gentiana calycosa ssp. obtusiloba, Gentiana calycosa ssp. xantha, Gentiana calycosa var. calycosa, Gentiana calycosa var. obtusiloba, Gentiana calycosa var. xantha, Pneumonanthe calycosa)