This section is from the book "An Illustrated Flora Of The Northern United States, Canada And The British Possessions Vol3", by Nathaniel Lord Britton, Addison Brown. Also available from Amazon: An Illustrated Flora of the Northern United States, Canada and the British Possessions. 3 Volume Set..
Erect, simple or branched, brown yellowish purplish or nearly white root-parasites, the leaves reduced to alternate appressed scales, the flowers perfect, irregular (rarely cleistogamous), sessile in terminal bracted spikes, or solitary and peduncled in the axils of the scales. Calyx inferior, gamosepalous, 4-5-toothed, 4-5-cleft, or split nearly or quite to the base on one or both sides. Corolla gamo-petalous, more or less oblique, the tube cylindric, or expanded above, the limb 2-lipped, 5-lobed. Stamens 4, didynamous, inserted on the tube of the corolla and alternate with its lobes, a fifth rudimentary one occasionally present; filaments slender; anthers 2-celled, the sacs parallel, equal. Ovary superior, 1-celled, the four placentae parietal; ovules numerous, antropous; style slender; stigma discoid, 2-lobed, or sometimes 4-lobed. Capsule 1-celled, 2-valved. Seeds numerous, reticulated, wrinkled or striate; embryo minute; cotyledons scarcely differentiated.
About 11 genera and over 200 species, of wide geographic distribution, mostly in the northern hemisphere.
Flowers all complete and perfect. Calyx 2-5-lobed or toothed.
Calyx about equally 5-cleft; no bractlets on peduncles nor calyx.
Calyx unequally toothed, or split on both sides; flowers bracteolate.
Calyx spathe-like, split on the lower side, 3-4-toothed on the upper.
Lower flowers cleistogamous, fertile; upper complete, mostly sterile.