This is a very difficult genus taxonomically, the species very similar to each other and often not easily recognizable, especially when individuals are small or immature.
The corollas are white or pale blue-purple, with darker purple lines and a bright yellow spot at the base of the lower lip.
1. Calyx, bracts, and leaves glabrous or at most scabrous on some nerves; calyx lobes and leaf teeth tapered into prolonged bristle tips.
1. Calyx, bracts, and leaves pubescent; calyx lobes acute to somewhat bristle-tipped.
2. Cauline leaves (not subtending flowers) strongly cuneate at base, the teeth acute to blunt; calyx pubescent principally on the nerves and lobes; plants sometimes flowering as low as the second node.
2. Cauline leaves broadly cuneate to rounded at base, the teeth rounded to blunt; calyx rather densely hairy throughout; plants flowering only as low as the fifth node.
All species found in Euphrasia
MICHIGAN FLORA ONLINE. A. A. Reznicek, E. G. Voss, & B. S. Walters. February 2011. University of Michigan. Web. February 21, 2019. https://michiganflora.net/genus.aspx?id=Euphrasia.