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..
[Actinella Nutt. (1818), not Pers. (1807), nor Actinea Juss. (1803).] Branched or scapose, villous-pubescent or glabrous, bitter and aromatic punctate herbs, with alternate or basal, often punctate leaves, and small or rather large, peduncled heads of both tubular and radiate, yellow flowers, or rays rarely wanting. Involucre hemispheric, campanulate or depressed, its bracts imbricated in 2-3 series, appressed. Receptacle convex or conic, naked. Ray-flowers pistillate and fertile, the rays 3-toothed, 4-nerved. Disk-flowers perfect, fertile, their corollas with 4-5-toothed limbs. Anthers entire or minutely sagittate at the base. Style-branches truncate and penicillate at the summit. Achenes turbinate, 5-10-ribbed or angled, villous or pubescent. Pappus of 5-12 thin aristate, acuminate or truncate scales. [Greek, four-nerved.]
About 18 species, natives of western North America and Mexico. Besides the following, some 12 others occur in the western and southwestern parts of the United States. Type species: Te. ra-neuris acaulis (Pursh) Greene. Stem leafy, branching; stem leaves linear; annual or biennial.
1. T. linearifolia.
Stems tufted, simple, scapose; leaves basal; perennials. Leaves narrowly linear; branches of the Caudex slender.
2. T. stenophylla.
Leaves broader, linear to spatulate; branches of the Caudex short and thick. Bracts of the involucre acutish.
3. T. acaulis.
Bracts of the involucre obtuse, rounded.
4. T. herbacea.
Annual or perhaps biennial; stem usually diffusely branched, finely hirsute, or glabrous, or woolly at the base, slender, 6'-15' high. Stem leaves narrowly linear, sessile, 1/2' - 1 1/2' long, 1/2" - 1" wide; basal leaves spatulate, often villous, much broader, obtuse, narrowed into margined petioles; heads numerous, slender-peduncled, 6"-8" broad; involucre broadly campanulate, its bracts oblong, obtuse, pubescent, distinct to the base, imbricated in about 2 series; receptacle conic; rays 6-10, oblong; achenes pubescent; pappus of 5 or 6 ovate awned scales.
In dry soil, Kansas to Louisiana, Texas and New Mexico. May-Sept.
Perennial with a branched caudex, the branches often 3 1/2' long, the upper portion covered with the scarious bases of old leaves. Bases of the leaves dilated, sparingly silky-villous; blades narrowly linear, 1' - 1 3/4' long, about 1" wide, glabrous, conspicuously punctate; scape 2' - 4' high, minutely strigose; involucre 5" - 7" wide; bracts oval or oblong-acutish; rays about 5" long and 2" wide.
In dry soil, Kansas to Colorado and Mexico. Formerly confused with T. scaposa (DC.) Greene.
Tetraneuris fastigiata Greene, of Kansas, differs by the leaf-bases and involucre being more densely pubescent; it is known only from imperfect specimens, and may not be distinct from T. stenophylla, over which it has priority of publication.
Gaillardia acaulis Pursh, Fl. Am. Sept. 743. 1814. T. acaulis Greene, Pittonia 3: 265. 1898. Actinella acaulis Nutt. Gen. 2: 173. 1818. Picradenia acaulis Britton, Mem. Torr. Club 5: 339.
1894. T. simplex A. Nelson, Bot. Gaz. 28: 127. 1899.
Perennial with thick roots and a stout branched caudex; scapes tufted, rather stout, or slender, densely silky or tomentose, 2'-8' high. Leaves all borne on the ends of the branches of the caudex, linear-spatulate, entire, obtuse or obtusish, 1' - 3' long, 1 1/2" - 3" wide, densely silky or villous; heads 9" - 18" broad; involucre hemispheric, its bracts densely villous, acutish; rays 10-15; pappus of 5 or 6, ovate or oblong, awned scales.
In dry or rocky soil, North Dakota to Assiniboia, Montana, Nebraska and New Mexico. May-Aug.
Tetraneuris scaposa (DC.) Greene, admitted into our first edition as from Nebraska, is not definitely known north of Texas.
T. herbacea Greene, Pittonia 3: 268. 1898. Actinia herbacea Robinson, Rhodora 10: 68. 1908.
Perennial by a stout thick caudex; scape stout, villous-pubescent, especially above, 6'-8' high. Leaves linear-spatulate, slightly fleshy, bluntish, strongly punctate, sparingly loosely long-hairy, at least toward the base, 2'-3' long, about 3" wide; heads nearly 2' broad; involucral bracts oblong, obtuse and rounded at the apex, densely villous; rays about 15; pappus scales ovate-oblong, obtuse, acute or apiculate.
Southern Ontario, Ohio and Illinois. May-June.