This section is from the book "British Wild Flowers - In Their Natural Haunts Vol5-6", by A. R. Horwood. Also available from Amazon: A British Wild Flowers In Their Natural Haunts.
Mr. Williams considers that this is the most marked species of the genus. " Its slender, erect form, small leaves and flowers, and usually dark-coloured stem and leaves are very marked characters." The stem is straight, slender, simple, sometimes branched in the middle. The leaves are small, shorter than the internodes, and are green or red, with few short hairs above and on the veins below. The stem-leaves are ovate, often wedge-shaped below, acute, with 6-8 acute teeth. The spike lengthens. The flowers vary in colour, as above, being white with blue lines, blue, or violet. The bracts are ovate or wedge-shaped below, with 6-10 awned teeth. The calyx is smooth, inflated, with lance-shaped teeth with a long point. The corolla is small, the upper lip having entire or faintly-toothed lobes. The capsule is linear to elliptic, blunt or notched, fringed with hairs.
Mr. F. N. Williams considers (ibid) that this plant is only distinguished from E. nemorosa in height, the dense soft hair, the afterwards slightly-lengthened spike, the size of the capsule (4-5 mm.), which is truncate or very slightly notched at the end. According to Townshend, whose descriptions are in the main followed here (they being based on Wettstein's), the stem is usually stout and branched below, the leaves are greyish-green, rough below, clothed with long bristles, the stem-leaves ovate, acute, with 8-14 acute teeth. The flowers are whitish or pale-lilac or blue. The bracts are sometimes nearly round, with 8-14 acute or shortly-awned teeth. The calyx is clothed with short white hairs on the margins and veins, and is somewhat inflated at length. The corolla is small, the lobes of the upper lip notched or with small teeth. The capsule is wedge-shaped to inversely ovate, blunt or notched, fringed with hairs.
By Mr. F. N. Williams this, species has been placed under E. arctica, Lange. The stem is straight, simple, or slightly branched at or below the middle, with long internodes. The leaves are long, densely clothed with stout white bristles and occasionally glandular hairs. The stem-leaves are few, ovate or wedge-shaped to inversely ovate, blunt, with 4-10 broad, blunt teeth. The spike is dense. The flowers are whitish. The bracts are broadly oval or nearly round, more or less blunt or acute, with a wedge-shaped base, with 6-12 broad, more or less blunt or acute teeth. The calyx has stout white bristles and glandular hairs, with broad acute teeth. The corolla is small, the lobes of the upper lip bent-back, with small teeth. The capsule is elliptic, notched, fringed with hairs.
Euphrasia fennica and E. suecica have recently been found in this country.