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..
Rudbeckia subtomentosa Pursh, Fl. Am. Sept. 575. 1814.
Densely and finely cinereous-pubescent and scabrous; stem branched above, 2°-6° high. Leaves thick, some or all of the lower ones deeply 3-lobed or 3-parted, petioled, 3'-5' long, the lobes oblong or lanceolate, acute or acuminate, dentate; upper leaves, or some of them, lanceolate or ovate, acuminate, sessile or nearly so; heads numerous, 2'-3' broad; rays 15-20, yellow, or with a darker base; disc subglobose, rounded, purple or brown, 6"-8" broad; bracts of the involucre linear-lanceolate, acuminate, squarrose, sweet-scented; chaff of the receptacle linear, obtuse or obtusish, pubescent, or somewhat glandular at the apex; pappus a short crenate crown.
On prairies and along rivers, Illinois to Louisiana, Kansas and Texas. July-Sept.
Rudbeckia hirta L. Sp. Pl. 907. 1753.
Hirsute or hispid throughout, biennial or sometimes annual; stems simple or sparingly branched, often tufted, 1°-3° high. Leaves thick, sparingly serrate with low teeth, or entire, lanceolate or oblong, the lower and basal ones petioled, mostly obtuse, 3-5-nerved, 2'-/ long, ¥-2' wide, the upper sessile, narrower, acute or acutish; heads commonly few or solitary, 2'-4' broad; rays 10-20, orange or orange-yellow, rarely darker at the base; bracts of the involucre very hirsute, spreading or reflexed, much shorter than the rays; disk globose-ovoid, purple-brown; chaff of the receptacle linear, acute or acutish, hirsute at the apex; style-tips acute; pappus none.
Prairies and plains, Ontario to Manitoba, Florida, Colorado and Texas. Widely distributed in the east as a weed, north to Quebec. Races differ in pubescence and in length and color of the rays. Nigger- or darkey-head. Nigger-or poor-land daisy. Golden-jerusalem. Yellow ox-eye-daisy. English bull's-eye. Brown daisy or betty. Brown-eyed susan. May-Sept.
Rudbeckia monticola Small, of the southern Alleghanies, with broader, ovate, acute or acuminate stem leaves, is recorded as extending northward into Pennsylvania.
Stem stout, hispid, erect, 11/2°-2 1/2° high, simple, grooved, leafy, at least below. Leaves serrate or crenate-serrate, strigose-pubescent, the basal ones ovate to ovate-lanceolate, 3-4' long, obtuse, long-petioled; stem leaves obovate to oval, often with a lateral lobe, the petioles wing-margined; uppermost leaves often ovate-lanceolate, sessile, cordate; bracts of the involucre foliaceous, often 1' long or more; head 2'-3' broad; rays about 12, 2-lobed; outer chaff oblanceolate, the inner linear, acute, purple-tipped, fringed with jointed hairs; style-tips slender, acute.
In woods, Pennsylvania to Virginia and Tennessee. May-July.