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..
Rough-hairy or prickly tall erect biennial or perennial herbs, with opposite dentate entire or pinnatifid, usually large leaves, and blue or lilac flowers in dense terminal peduncled oblong heads in our species. Bracts of the involucre and scales of the receptacle rigid or spiny pointed. Involucels 4-8-ribbed with a somewhat spreading border. Limb of the calyx cupshaped, 4-toothed or 4-lobed. Corolla oblique or 2-lipped, 4-lobed. Stamens 4. Stigma oblique or lateral. Achene free from or adnate to the involucel. [Greek, to thirst, the leaves of some species holding water.]
About 15 species, natives of the Old World. Type species: Dipsacus fullonum L. Scales of the receptacle straight-pointed.
1. D. sylvestris.
Scales of the receptacle hooked at the apex.
2. D, fullonum.
Dipsacus fullonum L. Sp. Pl. 97. In part. 1753. Dipsasus sylvestris Huds. Fl. Angl. 49. 1762.
Biennial, stout, with numerous short prickles on the stem, branches, peduncles, midribs of the leaves and involucre, otherwise glabrous or nearly so, 3°-6° high. Leaves sessile, or the upper ones con-nate-perfoliate, lanceolate or oblong, the upper acuminate and generally entire, the lower obtuse or obtusish, crenate or sometimes pinnatifid at the base, often 1° long; heads at first ovoid, becoming cylindric, at length 3'-4' long; flowers lilac, 4"-6" long; leaves of the involucre linear, curved upward, as long as the head or longer; scales of the receptacle ovate, tipped with a long straight subulate barbed awn, usually exceeding the flowers.
In waste places, Maine and Ontario to North Carolina, west to Michigan. Naturalized from Europe and native also of Asia. July-Sept. Other English names are Venus'-bath or -cup; wood- or church-brooms; shepherds'-staff; card- or water-thistle; gipsy-combs; hutton-weed. Indian's-thistle. Prickly-back. Adam's-flannel.
Dipsacus fullonum L. Sp. Pl. 97. 1753. Dipsacus fullonum var. sativus L. Sp. Pl. Ed. 2, 1677. 1763.
Similar to the preceding species. Leaves of the involucre, or some of them, shorter than the heads, spreading or at length reflexed; scales of the receptacle with hooked tips, about equalling the flowers, which are usually paler than in D. sylvestris.
About wool mills, Eastern and Middle States, rare. Fugitive from Europe, and perhaps nowhere permanently established within our range. Other English names are clothiers' brush, Venus'-bath or -cup. Generally regarded as probably a cultivated variety of the preceding species, as it is not found wild, except as an evident escape.
Dipsacus laciniatus L., with pinnatifid or bipinnatifid ciliate leaves, those of the involucre spreading, has been found at Albany, New York. Fugitive or adventive from Europe.