Gentiana affinis var. bigelovii (A. Gray) Kusnezow; G. affinis var. forwoodii (A. Gray) Kusnezow; G. affinis var. parvidentata Kusnezow; G. bigelovii A. Gray; G. forwoodii A. Gray; G. interrupta Greene; G. rusbyi Greene ex Kusnezow; Pneumonanthe bigelovii (A. Gray) Greene

Stems 1–5 dm. Leaves ± evenly spaced or occasionally more closely spaced proximally; blades all generally linear to lanceolate, narrowly oblong, or occasionally narrowly ovate, usually 3–15 mm wide, occasionally linear, 2–3 mm wide. Flowers: calyx tube uncleft or occasionally ± deeply cleft, lobes narrowly linear or occa­sionally some or all rudimentary, (0–)1–7(–10) mm; corolla (12–)18–30(–35) mm, lobes 3–5(–7) mm. 2n = 26.

Flowering late summer–fall. Mesic to wet meadows, prairies, river bars, open woods; 200–3900 m; Alta., B.C., Man., N.W.T., Sask.; Ariz., Colo., Idaho, Minn., Mont., Nev., N.Mex., N.Dak., Oreg., S.Dak., Tex., Utah, Wash., Wyo.

An old collection of var. affinis from Huron County, Ontario, presumably represents a chance introduction of short duration.

Variety affinis as circumscribed here includes some Colorado, New Mexico, and Wyoming plants with the distal leaves closely spaced, blades linear or nearly so, and relatively long. Such plants have sometimes been segregated as var. bigelovii or as Gentiana bigelovii. Studies for this flora, however, have indicated that although the extremes are distinctive in appearance, they intergrade with plants having the distal leaves more widely spaced and shorter, and do not appear to pre­dominate in any part of the range of G. affinis. Reports that the bigelovii vegetative morphology is associated with paler corolla color should be given further study.

Other taxonomic segregation, including the recog­nition of Gentiana interrupta, has been based on varia­tion in the density of the inflorescence, the number of nodes below the terminal inflorescence, if any, at which axillary cymules or flowering branches are borne, and the length of such branches. Studies for this flora have shown that there is extensive intergradation and little correlation of this variation with geographic distribu­tion. Some authors have treated plants with spathaceous, one- or two-cleft calyces with reduced or rudimentary lobes as G. affinis var. parvidentata, or have emphasized such calyces in their characterization of G. forwoodii. Plants with spathaceous calyces and var­ious degrees of reduction in the calyx lobes occur spo­radically throughout most of the range of the species, in populations otherwise referable to either of the two varieties recognized here, and may represent responses to growing conditions.

Occasional plants as far southeast as Wyoming approach var. ovata in leaf size and shape. Some rela­tively large-flowered plants in Arizona, New Mexico, and southern Utah, although here included in var. affinis, also approach var. ovata. Such more or less intermediate plants have sometimes been called Gentiana affinis var. major A. Nelson & J. F. Macbride. Some may represent the results of introgressive hybridization with G. parryi. Flower size and stem vestiture have been cited in dis­tinguishing G. rusbyi in Arizona and New Mexico, but the flowers of the type collection are not unusually large for G. affinis var. affinis. Plants from that region, whether or not relatively large-flowered, have at most only minute, papillate puberulence like that found among plants elsewhere in the range of G. affinis.

Variety affinis appears to have hybridized occasionally with Gentiana calycosa and G. puberulenta, although its variability makes the morphological recognition of hybrids uncertain.