THISTLE FAMILY 969 



toothed or lobed towards the apex, or the upper entire, glabrous and yellowish 

 green above, finely floccose beneath; heads many in a dense spike-like panicle; 

 involucre hemispheric, about 4 mm. high, 4^-5 mm. broad; bracts yellowish, only 

 sparingly floccose, ovate, oval, acutish, broadly scarious-margined; ray-flowers 

 5-7. Plains: Wash. n Ida. Son. Submont. 



29. A. arachnoidea Sheld. A perennial, with a branched rootstock or 

 caudex; stem 5-10 dm. high, striate, arachnoid-floccose; leaves linear-lanceo- 

 late, acuminate or acute, sessile, sparingly floccose but soon glabrate above, 

 permanently floccose beneath, 3-8 cm. long, the lower with a few lanceolate 

 short lobes; heads many, in a lax panicle, often sub-secund and nodding; involucre 

 hemispheric, about 4 mm. high and 6 mm. broad; bracts about 10, sparingly 

 floccose, yellowish green, ovate to elliptic, acute or obtuse, scarious-margined; 

 ray-flowers 8-10. Banks: Ore. Ida. Son. 



30. A. Hookeriana Besser. Tall perennial, with a rootstock; stem 3-6 dm. 

 high; leaves lanceolate or ovate in outline, glabrate above, densely white-tomen- 

 tose beneath, the upper entire, the lower deeply cleft into 3-7 lanceolate often 

 falcate divisions; heads numerous, in very dense elongate panicles, mostly erect; 

 involucre about 4 mm. high and 3 mm. broad, more or less tomentose; bracts 

 ovate to elliptic, obtuse, scarious-margined; ray-flowers 5 or 6. Valleys: Sask. 

 B.C. Ore. Plain. 



31. A. Douglasiana Besser. Stout perennial, with a rootstock; stem 6-10 

 dm. high; leaves numerous, 5-15 cm. long, lanceolate, acuminate, the lower more 

 or less lobed or toothed, with few lanceolate lobes or teeth, the upper ones entire, 

 all somewhat grayish-floccose above when young, permanently white-tomentose 

 beneath; heads numerous, at first nodding, in a large dense narrow leafy panicle; 

 involucre 4 mm. high, 3-4 mm. broad; bracts tomentose, at least when young; 

 the outer lanceolate, acutish, the inner elliptic, obtuse, broadly scarious-mar- 

 gined above; ray-flowers 6-8. A. vulgaris californica Besser. A. Kennedyi A. 

 Nels. Banks: Wash. Ida. s Calif. Son. Submont. 



32. A. Herriotii Rydb. Tall perennial, with a rootstock; stem simple, 6-10 

 dm. high, finely tomentose; leaves entire or sparingly and sharply toothed, 5-20 

 cm. long, glabrate and green above, densely white-tomentose beneath; heads 

 very numerous, erect, in a narrow dense panicle; involucre 4-5 mm. high, 2.5-3 

 mm. broad; bracts tomentose, the outer ovate-lanceolate, acute; inner bracts 

 elliptic, mostly obtuse; ray-flowers 6-8. Banks: Alta. Sask. S.D. Plain. 



33. A. ludoviciana Nutt. Perennial, with a cespitose rootstock; stem 

 usually branched, more or less tomentose, 3-6 dm. high; lower leaves oblanceolate, 

 3-7-lobed above the middle, 3-8 cm. long, soon glabrate and dark green above, 

 densely white-tomentose beneath; lobes lanceolate and falcate; upper leaves 

 lanceolate and entire; heads very numerous and small, in a compound open pan- 

 icle; involucres 3^4 mm. high, 2-3 mm. broad, usually densely tomentose; bracts 

 elliptic; corollas light brown. Prairies, canons, and mountain sides: Mo. Tex. 

 Ariz. Utah. Plain Submont. Au-S. 



34. A. cuneata Rydb. Perennial, with a creeping rootstock; stem 5-10 

 dm. high, tomentose, branched; leaves sessile, 2-4 cm. long, grayish floccose 

 above, white-tomentose beneath, those of the stem cuneate-obovate, pinnatifid, 

 or coarsely toothed towards the apex, the lobes or teeth ovate, often mucronate; 

 leaves of the inflorescence lanceolate and entire; heads numerous, hemispheric, 

 about 3 mm. broad; bracts oval, obtuse, tomentose, the inner scarious-margined; 

 ray-flowers 6 or 7. Banks: Colo. Tex. Son. Submont. Au-S. 



36. A. silvicola Osterhout. Perennial, with a creeping rootstock; stem 4-6 

 dm. high, slender, sparingly tomentose; leaves linear or linear-lanceolate, 4r-6 cm. 

 long, 3-8 dm. wide, entire or with a few sharp teeth, acuminate, glabrate above, 

 densely silvery-tomentose beneath; inflorescence loosely paniculate, 2-3 dm. 

 long; heads numerous, nodding; involucres about 5 mm. broad, tomentose, but 

 not very densely so; bracts oblong; ray-flowers 10-15. Mountains and prairies: 

 Tex. Colo. Utah Calif.; n Mex. Ariz. Ida. Son. Submont. Au-S. 



