Sp. Pl. 2: 604. 1753.
Herbs, annual [perennial]; hemiparasitic. Stems erect, not fleshy, retrorsely hairy. Leaves cauline, opposite; petiole absent or nearly so; blade sometimes fleshy, not leathery, margins crenate, serrate, dentate, or incised. Inflorescences terminal, subcapitate to diffuse spikes, flowers solitary in each axil; bracts present, subopposite or irregularly alternate. Pedicels present or absent; bracteoles absent. Flowers: sepals 4, calyx bilaterally symmetric, not flattened laterally, tubular, not accrescent in fruit, lobes triangular; petals 5, corolla white or cream to purple, lilac, violet, brownish purple, or yellow with violet veins (often without violet veins in E. subarctica) and yellow spot in throat and on abaxial lip, adaxial lip sometimes lilac, purple, or yellow, contrasting with rest of corolla, bilabiate, funnelform, abaxial lobes 3, emarginate, adaxial 2, adaxial lip cucullate; stamens 4, didynamous, filaments glabrous, anther mucros unequal; staminode 0; ovary 2-locular, placentation axile; stigma capitate. Capsules: dehiscence septicidal, opening in distal 1/2, margins ciliate, sometimes glabrous or short-ciliate (E. salisburgensis). Seeds 10–18, grayish, fusiform, wings absent. x = 11.
North America, South America, Eurasia, Africa (Morocco), Atlantic Islands (Azores, Iceland), Pacific Islands (Oceania), Australia.
Species ca. 350 (18 in the flora).
Euphrasia is distributed throughout temperate regions of the northern and southern hemispheres, with one transtropical connection across the high mountains of Oceania. All Euphrasia species in the flora area belong to sect. Euphrasia, the largest of 15 sections in the genus (G. Gussarova et al. 2008). The section is noted for its taxonomic complexity. Major factors explaining the complex patterns of variation in sect. Euphrasia include interspecific hybridization, recent radiations, parasitism, polyploidization, and breeding system transitions (T. Karlsson 1974, 1986; P. F. Yeo 1978; G. C. French et al. 2008; R. A. Ennos et al. 2012). All North American species are tetraploids except, probably, E. disjuncta, E. farlowii, E. oakesii, E. randii, and E. subarctica. Of 18 species in the flora, nine are considered endemic. To facilitate identification of the species, the aggregate species concept is sometimes used to show relationships among the so-called more conventional, discrete taxa (Gussarova 2005). Following that concept, four aggregate species are represented in the flora area and their associated species treated here are: E. borealis (F. Townsend) Wettstein agg. (species 3 and 4), E. nemorosa agg. (species 6–10), E. oakesii agg. (species 13–15), and E. minima Jacquin ex de Candolle agg. (species 16 and 17).
The key makes no provision for hybrids, which often have intermediate features or a mixture of character states typical of their putative parental species. For a reliable identification, multiple representative plants should be collected and examined from a population to account for individual variation in key characters. The bracts referred to in the key are proximal floral leaves, which are most representative of the variation along the stem. The teeth of the bracts become progressively more acute up the stem as well as on any one leaf from apex to base. To characterize teeth shape, the key uses the most basal ones. Sessile glands are often present on the abaxial surface of bracts; they have no taxonomic value. Glandular (on short versus long stalks) and eglandular hairs are used in characterizing indumentum of different species.
Two infraspecific levels are used in this treatment. This is consistent with the usage in other Euphrasia treatments (for example, P. F. Yeo 1978). Subspecific rank is used for geographic or ecological integrity; varietal rank is used to indicate transitions between the extreme forms without any geographic or ecological distinction.
|1||Bracts oblong to lanceolate, lengths 2.5+ times widths; capsule margins eciliate or short-ciliate.||Euphrasia salisburgensis|
|1||Bracts ovate, obovate, deltate, suborbiculate, elliptic, oval, oblong-ovate, or oblong, lengths not more than 2 times widths; capsule margins conspicuously long-ciliate.||> 2|
|2||Bract surfaces hairy, hairs glandular (with stalks sometimes flexuous, 3–6-celled, 0.2–0.6 mm).||> 3|
|3||Stems simple, sometimes with 1 or 2 pairs of branches; corollas 3–4 mm, white to yellow; Alberta, British Columbia, Manitoba, Northwest Territories, Saskatchewan, Yukon, Alaska, Montana.||Euphrasia subarctica|
|3||Stems simple or with 1–6 pairs of branches; corollas 4–5.5 mm, white; Newfoundland and Labrador, Nova Scotia, Nunavut, Quebec, Maine.||Euphrasia disjuncta|
|2||Bract surfaces glabrous or hairy, hairs eglandular or glandular (with stalks 1- or 2-celled, 0.1–0.2 mm).||> 4|
|4||Bract surfaces hairy, hairs glandular.||> 5|
|5||Inflorescences beginning at nodes (5–)7–9(–11); corollas 8–10 mm; capsules narrowly oblong, apices truncate to retuse; usually pastures, scrub, marshy places.||Euphrasia stricta|
|5||Inflorescences beginning at nodes 2–4; corollas 5–8(–10) mm; capsules oblong to elliptic or obovate, apices truncate, retuse, or emarginate; usually coastal.||> 6|
|6||Bract teeth much longer than wide, apices acute to acuminate; corollas 6–8(–13) mm.||Euphrasia arctica|
|6||Bract teeth as long as or slightly longer than wide, apices subacute to acute, rarely aristate; corollas 5–8 mm.||Euphrasia frigida|
|4||Bract surfaces glabrous or hairy, hairs eglandular.||> 7|
|7||Corollas yellow.||> 8|
|8||Corollas 3–4 mm; leaf blades oblanceolate to broadly ovate; bract surfaces sparsely hirsute.||Euphrasia subarctica|
|8||Corollas 4–5.5 mm; leaf blades ovate to orbiculate; bract surfaces densely hirsute.||Euphrasia mollis|
|7||Corollas white, cream, lilac, violet, purple, or brownish purple.||> 9|
|9||Bracts elliptic to ovate, bases strongly cuneate, tooth apices acute, sometimes aristate.||Euphrasia hudsoniana|
|9||Bracts oval, ovate to obovate, suborbiculate, deltate, or oblong-ovate, bases round, truncate, or cuneate, tooth apices obtuse, acute, or subacute, rarely aristate.||> 10|
|10||Corollas 6–11(–13) mm.||> 11|
|11||Inflorescences beginning at nodes 3–5.||Euphrasia arctica|
|11||Inflorescences beginning at nodes (5–)7–9(–11).||Euphrasia stricta|
|10||Corollas 2.5–7.5(–8.5) mm.||> 12|
|12||Sinuses between teeth rounded, bract tooth apices obtuse or acute; corollas purple or lilac with darker lines.||Euphrasia oakesii|
|12||Sinuses between teeth acute, bract tooth apices obtuse, subacute, or acute, rarely aristate; corollas white, cream, lilac, violet, or brownish purple, rarely purple.||> 13|
|13||Inflorescences capitate, beginning at nodes 4 or 5; calyx lobes falcate, apices obtuse.||Euphrasia oakesii|
|13||Inflorescences sparsely or densely spicate, beginning at nodes 2–12; calyx lobes straight, apices acute.||> 14|
|14||Inflorescences densely spicate, sometimes 4-angled.||Euphrasia tetraquetra|
|14||Inflorescences sparsely spicate, not 4-angled.||> 15|
|15||Inflorescences beginning at nodes 2–5; stems with 0–2 pairs of branches; arctic regions, sometimes non-arctic regions.||> 16|
|16||Capsules 6–8 mm, elliptic to obovate, equal to or slightly longer than calyces, apices emarginate.||Euphrasia wettsteinii|
|16||Capsules 4–6 mm, oblong to narrowly elliptic, shorter than or equal to calyces, apices retuse.||Euphrasia vinacea|
|15||Inflorescences beginning at nodes 3–12; stems with 0–7 pairs of branches; non-arctic regions or, if arctic, inflorescences usually beginning at nodes 5+.||> 17|
|17||Bracts suborbiculate, broadly ovate, or oblong-ovate, surfaces +/- densely hirsute, teeth shorter than or as long as wide, apices obtuse or subacute to acute.||> 18|
|18||Stems to 12(–15) cm; bract teeth as long as wide.||Euphrasia ostenfeldii|
|18||Stems to 27(–37) cm; bract teeth shorter than wide.||Euphrasia suborbicularis|
|17||Bracts ovate to obovate, oblong, or oval, surfaces glabrous or hirsute, teeth longer than or as long as wide, apices obtuse to acute, sometimes aristate.||> 19|
|19||Corollas 4.5–7.5(–8.5) mm.||> 20|
|20||Corollas 5–7.5(–8.5) mm; bracts not glossy, surfaces glabrous or hirsute, tooth apices acute, sometimes aristate.||Euphrasia nemorosa|
|20||Corollas 4.5–6.5 mm; bracts glossy, surfaces glabrous, tooth apices acute.||Euphrasia micrantha|
|19||Corollas 3–5.5 mm.||> 21|
|21||Stems branched from middle and/or distal cauline nodes, branches erect; cauline internode lengths (1–)2–5 times subtending leaves; inflorescences: proximal internode lengths 0.8–3(–4) times bracts.||> 22|
|22||Stems simple, sometimes branched, branches 1 or 2 pairs; corollas 3–4 mm, white to yellow; Alberta, British Columbia, Manitoba, Northwest Territories, Saskatchewan, Yukon, Alaska, Montana.||Euphrasia subarctica|
|22||Stems simple or branched, branches 1–6 pairs; corollas 4–5.5 mm, white; Newfoundland and Labrador, Nova Scotia, Nunavut, Quebec, Maine.||Euphrasia disjuncta|
|21||Stems branched from basal, middle, and/or distal cauline nodes, branches ascending; cauline internode lengths 1–3(–5) times subtending leaves; inflorescences: proximal internode lengths 0.8–1.5 times bracts.||> 23|
|23||Cauline internode lengths 1–3(–5) times subtending leaves; bracts 2–7 mm, abaxial surfaces setulose on veins, adaxial puberulent.||Euphrasia randii|
|23||Cauline internode lengths 1–2 times subtending leaves; bracts 2–4 mm, surfaces coarsely, densely hirsute.||Euphrasia farlowii|