1a. Stem leaf blades 1.1-3.6 cm wide. Basal leaf blade margins crenate, serrulate, serrate or occasionally entire (occasionally several of these on the same plant)..........2
1b. Stem leaf blades 0.5-2 cm wide. Basal and stem leaf blade margins entire or serrulate.........3
2a. Basal and stem leaf blade bases usually attenuate and unequally tapered. Petals deep lemon-yellow. Occasionally the upper 2-4 petals are brownish-purple behind..........Viola praemorsa ssp. linguaefolia
2b. Basal and stem leaf blade bases usually more or less truncate to subcordate. Blades generally ovate, basal 2.3-6.7 cm long, not much longer than wide. Stem blades 1.3-3 cm wide. Petals deep lemon-yellow. Occasionally the upper 2-4 petals are brownish-purple behind..........Viola praemorsa ssp. praemorsa
3a. Basal blades lanceolate, oblanceolate, or elliptic. Rarely ovate. Leaf base generally attenuate and unequally tapered. Blades to 8.8 cm long with attenuate bases. Margins generally entire and ciliate. Petals deep lemon-yellow, the upper pair often brownish purple behind, the lower trio often streaked with dark brown to brownish purple........Viola bakeri
3b. Basal blades ovate to oblong-ovate and up to 4.3 cm long. Base of leaf usually attenuate to more or less truncate. Margins entire to serrulate, occasionally sinuate or ciliate. Petals deep lemon-yellow, the upper pair often brownish purple behind, the lower trio often streaked with dark brown to brownish purple.........Viola vallicola var. major