COMPOSITAE. IOO9 



Annual, or perhaps biennial, with a branching stem. r. T. linearifolia. 



Cespitose scapigerous perennials with all the leaves basal. 



Branches of the caudex comparatively slender and elongated; leaves narrowly linear, 

 the blade much narrower than the dilated base. 



Bases of the leaves and involucre sparingly silky-villous. 2. T. stenophylla. 



Bases of the leaves conspicuously arachnoid hairy; involucre densely villous. 



3. T.fastigiata. 



Branches of the caudex very short and thick ; leaves from linear to spatulate, but 

 the blade not much narrower than the base if at all. 



Bracts of the involucre acutish, densely silky; leaves decidedly silky. 



Leaves linear or narrowly oblanceolate, 4-7 cm. long. 4. T. simplex. 



Leaves oblanceolate or spatulate, 2-4 cm. long. 5. T, acaulis. 



Bracts of the involucre rounded, obtuse, sparingly silky; leaves nearly glabrous. 



6. 7\ herbacea. 



1. Tetraneuris linearifolia (Hook.) Greene. FINE-LEAVED TETRANEURIS* 

 (I. F. f. 3968.) Annual or perhaps biennial; stem usually diffusely branched' 

 finely hirsute, or glabrous, or woolly at the base, slender, 15-35 cm. high. Stem' 

 leaves narrowly linear, sessile, 1-4 cm. long, 1-2 mm. wide; basal leaves spatulate' 

 often villous, much broader, obtuse, narrowed into margined petioles; heads 

 numerous, slender-peduncled, 12-16 mm. broad; involucre broadly campanulate, 

 its bracts oblong, obtuse, pubescent, imbricated in about 2 series; receptacle conic; 

 rays 6-10, oblong; achenes pubescent; pappus of 5 or 6 ovate awned scales. In 

 dry soil, Kans. to La., Tex. and N. Mex. May Sept. \Picradenia linearifolia 

 (Hook.) Britton. 



2. Tetraneuris stenophylla Rydb. NARROW-LEAVED TETRANEURIS. Per- 

 ennial with a branched caudex; branches of ten 5-8 cm. long, upper portion covered 

 with the scarious bases of old leaves; bases of the leaves dilated, sparingly silky- 

 villous; blades narrowly linear, 3-4 cm. long, 1-2 mm. wide, glabrous, conspicu- 

 ously punctate; scape 6-10 cm. high, minutely strigose; involucre 10-13 mm - 

 wide; bracts oval or oblong-acutish ; rays about 10 mm. long and 4 mm. wide. In 

 dry soil, Kans. to Colo, and Mex. \Actinella glabra T. & G., not Nutt.; Picra- 

 denia scapes a Britton, 111., Fl., in part.] 



3. Tetraneuris fastigiata Greene. FASTIGIATE TETRANEURIS. Like the 

 preceding, but leaves still narrower, about I mm. wide, the bases conspicuously 

 arachnoid villous; involucre about 8 mm. wide; bracts ovate, densely villous. Only 

 known from the imperfect type material from dry hills near Coolidge, Kans. 



4. Tetraneuris simplex A. Nelson. SIMPLE TETRANEURIS. Cespitose per- 

 ennial; caudex with very short thick erect branches ; scapes few, 1-2 dm. high, silky- 

 strigose; leaves linear or linear-oblanceolate, silky but less so than in the next, 47 

 cm. long, 2-5 mm. wide; involucre 15-18 mm. wide, its bracts oblong-lanceolate, 

 acute, densely silky-villous; rays about I cm. long. On dry hills, Black Hills of 

 S. Dak., western Neb., Wyo. and Mont. June-July. 



5. Tetraneuris acaulis (Nutt.) Greene. STEMLESS TETRANEURIS. (I. F. f. 

 3970.) Similar to the preceding species, perennial by thick roots and a stout 

 branched caudex; scapes tufted, densely silky or tomentose, 5-15 cm. high. Leaves 

 all borne on the ends of the branches of the caudex, spatulate, entire, obtuse or 

 obtusish, 3-5 cm. long, 3-6 mm. wide, densely silky or villous; heads 18-35 mm - 

 broad; involucre hemispheric, its bracts densely villous; rays 10-15; pappus of 5 

 or 6 ovate or oblong awned scales. In dry or rocky soil, N. W. Terr, to Mont., 

 Neb., Ariz, and N. Mex. May- Aug. [Picradenia acaulis (Nutt.) Britton.] 



6. Tetraneuris herbacea Greene. GREEN TETRANEURIS. Perennial, with a 

 rather simple caudex; scape stout, 10-15 cm. high, strigose-silky; leaves narrowly 

 oblanceolate, 5-8 cm. long, 4-8 mm. wide, at first sparingly long-silky, soon gla- 

 brous and green; involucre about 16 mm. wide, its bracts oblong, rounded, obtuse, 

 sparingly silky; rays 15 mm. or more long, 20-25 ^ n number. Hills, Ohio and 111. 

 May-June. 



78. PICRADENIA Hook. 



Branched, more or less pubescent plants with alternate, pinnately divided leaves 

 with linear segments and peduncled radiate heads with yellow flowers. Involucre 

 hemispheric, its bracts in 2 series, the outer ones united at the base. Receptacle 

 convex or conic, naked. Ray-flowers pistillate and fertile, usually 3-toothed, 



