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..
Cuscuta Epithymum Murr. in L. Syst. Ed. 13, 140. 1774. Cuscuta Trifolii Bab. Phytol. 1: 467. 1843.
Stems filiform, red; flowers sessile in small dense clusters, pinkish, about 1" long. Calyx variable, 4-5-lobed, more than one-half the length of the cylin-dric corolla-tube, the lobes acute; corolla 4-5-lobed, the lobes erect, about one-half as long as the tube, acute, its scales strongly incurved, crenulate nearly or quite to the base; stigmas filiform; capsule cir-cumscissile, capped by the withering corolla.
Usually on clover, Maine and Ontario to South Dakota and Pennsylvania. Introduced from Europe, where it occurs on thyme, clover and other low plants. Hail-weed. Hairweed. July-Sept.
Cuscuta europaea L., another Old World species, with obtuse calyx-lobes and shorter styles, is recorded from Maine.
Cuscuta arvensis Beyrich; Hook. Fl. Bor. Am. 2: 77. As synonym. 1834.
Plant pale yellow; stems filiform, the flowers nearly sessile in small clusters. Calyx broad, 5-lobed, the lobes broad, obtuse; corolla nearly campanulate, 5-lobed, the lobes acute or acuminate, as long as the tube, their tips reflexed, its scales large, ovate, as long as or longer than the tube, densely fringed all around with short irregular processes; stamens not ex-serted; style shorter than the ovary; stigmas capitate; capsule depressed-globose, indehis-cent, the withering corolla and usually the stamens persistent at it's base.
On various herbs and low shrubs, Massachusetts to Manitoba, Florida, Texas, Mexico and California. Also in the West Indies and South America. July-Aug.
Cuscuta Polygonorum Engelm. Am. Journ. Sci. 43:
Plant orange-yellow; stems slender but rather coarse; flowers sessile or nearly so in dense clusters. Calyx short, 4-5-lobed, the lobes ovate-oblong, acute or acutish; lobes of the corolla 4 or 5, triangular-ovate, acute, mostly as long as the tube, the scales usually obsolete, wanting, or consisting of only 2 or 3 slender processes on each side of the attached lower portion of the filament; filaments mostly slender; styles shorter than the ovary; stigmas capitate; capsule globose, the withering corolla persistent at its base.
On Polygonum and other herbs, Pennsylvania and Delaware to Minnesota, Wisconsin and Arkansas. July-Sept. Has been referred to the South American C. obtusiflora H. B. K.