This family consists of root parasites or hemiparasites, either lacking chlorophyll and thus wholly dependent on their hosts, or with some green leaves. Many species turn black on drying. Some parasitic species are important agricultural pests in the Old World. The green hemiparasitic species were included in the Scrophulariaceae in Michigan Flora.
1. Plants non-green, leaves converted to small, non-photosynthetic bracts.
2. Flowers in a dense, thick, scaly spike, the bracts subtending them 3–8 mm broad and nearly or quite exceeding the calyx; stem below the inflorescence ca. 4–10 mm thick, ± densely covered with bract-like leaves at least as large as the floral bracts; stamens exserted.
2. Flowers solitary or well separated, their bracts at the bases of long pedicels or up to 2 mm wide and scarcely touching the calyx; aerial stems if any 1.5–4.5 (–6) mm thick below the inflorescence, with scattered bracts; stamens sometimes exserted (Epifagus) or included in the corolla (Orobanche).
3. Pedicels none or much shorter than the flowers, essentially glabrous; flowers ca. 11 mm long or a little shorter, blooming in late summer or early fall; stem often much-branched; calyx glabrous or nearly so, the lobes ± deltoid and glandular along the margin.
3. Pedicels equaling or exceeding the flowers, densely glandular-pubescent on all sides; flowers 1.6–2.5 cm long, blooming in early to mid-summer; stems unbranched; calyx glandular-pubescent, the lobes ± acuminate.
1. Plants green, leaves present and photosynthetic, green or sometimes strongly tinged with purple (often blackening upon drying).
4. Cauline leaves all or mostly alternate on fertile stems (lowermost leaves sometimes opposite and rosette of larger basal leaves sometimes present).
5. Corolla ca. half or more covered by the calyx; bracts of inflorescence cream, yellow, or red at least apically; leaves entire or with a few irregular, thin, long lobes.
5. Corolla much less than half covered by the calyx; bracts greenish; leaves deeply regularly pinnately lobed.
Pedicularis (in part)
4. Cauline leaves all or mostly opposite (rarely whorled) on fertile stems (may be alternate immediately beneath flowers).
6. Leaves (especially middle and lower ones) deeply pinnately toothed or lobed ca. 1/3 or more the distance to the midrib; corolla yellow or cream, ca. 1.5–5 cm long.
7. Flowers in dense spike-like racemes at the ends of stems and branches; stamens ± enclosed in the hooded upper lip of corolla; calyx and corolla both strongly 2-lipped.
7. Flowers axillary or in racemes; stamens not enclosed in upper corolla lip; calyx and corolla 5-lobed but only weakly 2-lipped.
8. Corolla ca. 2.5–4.5 cm long; flowers on pedicels 2–13 mm long; calyx glabrous or with glandular or eglandular pubescence.
Aureolaria (in part)
8. Corolla ca. 1.5 cm long; flowers nearly sessile (pedicels ca. 2 mm or less); calyx with eglandular pubescence.
6. Leaves of main stem toothed or entire but not so deeply pinnately toothed or lobed (uppermost leaves or bracts may have small basal lobes); corolla yellow or not.
9. Flowers (all or many of them, especially lower ones) in the axils of alternate bracts in a distinct terminal or racemose inflorescence.
10. Corolla 15–22 mm long; calyx lobes ca. 1/3 as long as tube, or shorter; leaves (at least the larger ones) (3–) 4–8 cm long.
10. Corolla ca. 10 mm long or shorter; calyx lobes ca. half as long as tube; leaves not over 3 cm long.
11. Leaves ± palmately veined (with 3–5 prominent veins from the base), less than twice as long as wide; mucros at end of anther sacs very unequal (one much longer than the others); corolla glabrous or ± pubescent on the outside.
Euphrasia (in part)
11. Leaves pinnately veined (with a prominent midrib), 3–6 times as long as wide; mucros at ends of anther sacs equal in length; corolla uniformly and densely puberulent on the outside.
9. Flowers all solitary in the axils of opposite (or whorled) leaves or bracts.
12. Corolla strongly 2-lipped and bilaterally symmetrical, the upper lip and lower lip differentiated in size and shape.
13. Leaves less than twice as long as broad, mostly sessile.
Euphrasia (in part)
13. Leaves ca. 3–16 (–26) times as long as broad, including petiole, if any.
14. Main stem leaves entire or obscurely few-toothed; flowers white with the floor of the lower lip yellowish; calyx not papery and inflated.
14. Main stem leaves strongly toothed; flowers bright yellow; calyx papery and strongly inflated, especially in fruit.
12. Corolla nearly regular, the 5 lobes all about the same size and shape.
15. Corolla pink to purple (white in albinos), ca. 0.8–2.6 cm long; calyx and other parts glabrous (at most scabrous) or with hairs of distinctly different lengths.
15. Corolla bright yellow; ca. 3–4 cm long; calyx tube, pedicels, and stems with hairs of uniform length.