THISTLE FAMILY 1001 



heads 8-15; involucres 8-10 mm. high, campanulate; bracts shorter than the 

 disk; achenes striate, glabrous. Perhaps not distinct from S. colamhianus. Wet 

 places: Wyo. — Colo. — Utah — -Ida. Subinont. — Subalp. Je-Au. 



111. S. solitarius Rydb. Stem glabrous, 3-4 dm. high; lower leaves thin, 

 glabrous, wing-jietioled; blades oval, subentire, about 5 cm. long; middle leaves 

 lanceolate, clasping at the base, the uppermost reduced, Unear-lanceolate or 

 subulate; heads solitary, about 2 cm. high; bracts narrowly linear, black-tipped; 

 ligules light yellow, almost 1.5 cm. long; achenes glabrous. Meadows: n Wyo. 



112. S. megacephalus Nutt. Stout, more or less floccose perennial, with 

 a thick rootstock; stem simple; leaves oblong, oblanceolate, or linear, 1-2 dm. 

 long, rather thick, entire-margined or merely denticulate; heads solitary or sel- 

 dom 2-3, 1.5-20 mm. high and about 1.5 cm. broad; bracts linear, thick, acumin- 

 ate, often surpassed by the subulate calycidate ones; disk light brownish yellow; 

 ligules orange, 1.5-20 mm. long; achenes glabrous. Mountain regions: Ida. — 

 Mont.— Alta.— B.C. Mont.— Subalp. Jl-Au. 



113. S. vulgaris L. Annual; stem erect, 1-4 dm. high, more or less pilose 

 or glabrate; leaves sinuate-pinnatifid, glabrous or slightly arachnoid, with oblong 

 to rounded incised divisions, the upper auriculate-clasping; heads cymose; invo- 

 lucres campanulate-cylindric, 7-9 mm. high, glabrous; bracts linear-subulate, 

 black-tipped, the calj'culate ones minute; rays none; achenes canescent-puberu- 

 lent. Waste places: Lab. — Newf. — N.C. — Calif. — Alaska; nat. from Eu. F-Au. 



114. S. palustris (L.) Hook. Stem arachnoid-villous when young, 1.5-5 

 dm. high, rather fleshy, strongly striate; lower leaves with winged petioles; blades 

 lanceolate in outline, sinuately dentate to laciniate-pinnatifid, the upper linear, 

 more or less clasping; cyme crowded, corymbiform; involucres hemispheric, 

 about 8 mm. high, not calvculate; bracts narrowly linear-lanceolate, acuminate; 

 ligules broad and short, oblong, light yellow, 4-5 mm. long; achenes glabrous. 

 Wet ground: Lab. — la. — Sask. — Alaska and the Arctic coast; Eu. Subboreal 

 — Subardic. My-Jl. 



130. TETRADYMIA DC. 



Low and rigid shrubs; leaves or branches, or both covered with white perma- 

 nent or deciduous tomentum. Leaves alternate, entire, with smaller secondary 

 ones fascicled in their axils, or the primary leaves modified into spines. Heads 

 discoid. Involucre cylindric or oblong; bracts 4-6, concave, overlapping. Re- 

 ceptacle small, flat, naked. Corolla with elongate cylindric tube and lanceo- 

 late, spreading lobes longer than the short campanulate throat. Anthers sagit- 

 tate at the base, with triangular tips. Style-branches flat, with short obtusely 

 conical tips. Achenes terete, 5-nerved, short. Pappus of numerous fine, white, 

 minutely scabrous bristles. 



Heads 4-flowered; bracts 4, lance-oblong; branches with scurvy-toinentose lines. 



Primary leaves linear to oblanceolate, permanently tomentose, more or less spreading. 

 Primary leaves oblanceolate. 1. T. inermis. 



Primary leaves linear. 



Primary leaves 2-3 cm. long, straight. 2. T. canescens. 



Primary leaves 1-1.5 cm. long, arcuately recurved, pungent-pointed; secondary 

 leaves fascicled. 3. T. linearis. 



Primary leaves linear-subulate. 



Primary leaves erect, slender; secondary leaves linear, or spatulate-linear, glabrate 



in age. 4. T. glabrata. 



Primary leaves spreading, stiff, spine-like; secondary leaves oblanceolate. 



5. r. Nuttallii. 

 Heads 5-9-flowered ; bracts 5-6, at least the inner broadly oval ; branches wliite-tomentose 

 throughout; plant spiny. 

 Spines 5-12 mm. long, more or less curved. 6. T. spinosa. 



Spines 15-30 mm. long, straight. 7. T. lonyispina. 



1. T. inermis Nutt. Shrub, 2-5 dm. high; branches canescent, short and 

 crowded, very leafy; primary leaves oblanceolate or Hnear-oblanceolate, white- 

 tomentose, 1-4 mm. long; heads about 1 cm. high; involucres cylindric; bracts 

 4, white-tomentose, linear-oblong, obtuse, somewhat carinate; achenes silky- 

 canescent. T. multicaulis A. Nels., a dwarf form, merely suffruticose at the 

 base. Alkaline flats and stony ridges: Mont. — Colo. — Utah — Nev. Plain— 

 Mont. JKS. 



