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.
This plant is a saprophytic parasite, and the habitat is that of the plants it grows upon, roots of shrubby Papilionaceae as Gorse and Broom, etc, pastures and heaths, or commons. The stem is erect, brown, stout, leafless. The corolla is dull-yellow, more or less bell-shaped, gaping-, only the base remaining after flowering. The stamens are inserted at the base of the tube, and the anther-stalks are hairy above, smooth below. The spike is dense. The upper lip is arched, entire, the lower middle lobe longer than the side lobes. The anthers are white when dry. The stigma consists of 2 distant yellow lobes. The valves of the capsule cohere at each end. The seeds are numerous. The plant is 1-3 ft. in height, and flowers between June and August, being perennial.
The habitat of this plant is that of Wild Thyme, upon which it is a parasite, or heaths. The habit is that of a parasite. The plant is sweet-scented, and red in colour (hence rubra). There are no leaves, and the aerial stem is a scape. The flowers are borne in a loose spike. The sepals are 1-veined, or with a second faint one near the anterior margin, entire, lance-shaped, or awl-like, narrow, longer than the tube of the corolla. The corolla is dull-red, as long as, or shorter than, the bracts, bell-shaped, with a broad, curved tube, with small lobes. The upper nearly entire or notched lip is arched, glandular, downy within. The lips are toothed and crisped. The lateral lobes of the lower lip are nearly equal, and the middle lobe is rather long. The stamens are inserted near the base of the tube. The anthers are brown when dry. The anther-stalks are hairy below, glandular above. The stigma is pale-red, divided into 2 lobes. The plant is 4-9 in. in height, flowering between June and August, and is a herbaceous perennial.