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.
The habitat of this plant is woods and thickets, or damp shady places, where it is parasitical on the roots of hazel, etc. The habit is erect, that of a parasite. Both the branched rhizome and scapes bear scales, those on the rhizome thick and fleshy, and folded back on themselves. The leaves have undulating chambers, with glands of two kinds, the one club-shaped, 2-celled, stalked, in the other the cells are like a flat dome. The cells bear filaments which entangle and capture animals that enter the chambers, digesting their juices. The rootlets are attached to the roots of the host by tubercles. The plant is flesh-coloured or bluish, with purple streaks. The scapes are stout. The flowers are dull purple or white in bent-down racemes, one-sided, the flowers nearly stalkless. The bracts are entire, egg-shaped, lance-shaped. The calyx is 2-lipped. The lower lip of the arched corolla is divided into three, the upper entire or divided nearly to the base into two lobes. The anthers are united and covered with hairs. The style projects, and is bent down or straight, and the stigma is purple. The capsule is egg-shaped. The plant is 4-10 in. high, flowering in April and May, and is perennial.