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 woodlands, where it is parasitic on trees - Hawthorn, Apple, Poplar, rarely on Oak. It is a parasite, with the shrub habit. The branches are smooth, yellowish-green, rounded, dividing into two regularly, knotted. The yellow-green colour is supposed to be due to the plant being nourished by the descending sap, which is partly elaborated, and green leaves are thus dispensed with. But the leaves undoubtedly manufacture carbohydrates in winter in the ordinary way, and the root is fixed in the host so that it receives both the ascending and the descending sap. The plant thus establishes a symbiotic relationship. The leaves are broader in the male plant, opposite or in whorls inversely egg-shaped or lance-shaped, blunt. The flowers are green, the males in threes, the females in fives, in axillary clusters, stalkless. The berries are rounded, clammy, white, transparent, 1-seeded, crowned with the calyx. The plant is 1-3 ft. in height, flowering from February to May, and is an evergreen shrub.