THISTLE FAMILY 893 



herbaceous tips, imbricate in several series; receptacle pitted, the pits with toothed 

 or lacerate edges. Ray-flowers numerous, pistillate; ligules violet or puri)le. 

 Disk-flowers perfect; corollas yellow, turning red or brown. Anthers rounded 

 at the base. Style-branches with subulate or lanceolate, acute appendages. 

 Achenes turbinate, pubescent or glabrate. Pappiis of numerous firm rough 

 bristles. 



Leaves once or twice pinnatifid; root annual; achenes terete. 

 Green tips of the bracts short, not SQuarrose. 



Heads G-7 mm. high; plant 3-5 dm. high. 1. M. parviflora. 



Heads about 1 cm. high; plant low, 1-2 dm. liigh. 2. M. humilis. 



Green tips of the bracts long, reflexed-squarrose. 3. M, tanaceti folia. 



Leaves spinulose-toothed ; plant perennial or biennial; achenes compressed. 



Bracts linear-subulate; green tips in most longer than the straw-colored lower portion, 



squarrose reflexed. 

 Stem and inflorescence distinctly viscid. 



Stem-leaves lanceolate or oblong, usually distinctly triple-veined. 



Leaves tliin, coarsely but not saliently dentate; bracts Over 1 nun. wide. 



4. M, Bigelovii. 



Leaves thick with salient teeth; plant very glandular; bracts less than 1 



nun. wide. 

 Achenes glabrous or minutely pubescent; stem glabrous below. 



5. M.rarians. 



Achenesstrigose; stem glandular -hispid throughout. 6. M. aspera. 



Stem-leaves Unear or oblanceolate, 1-nerved. 



Plant 3-5 dm. high; heads numerous in a panicle or raceme. 



7. Af. viscosula. 



Plant 1-2 (seldom 3) dm. high; heads solitary or few, 8. M. Patlcrsonii. 



Stem strigose-puberulent; involucre slightly if at all viscid. 



Leaves all saliently toothed; inflorescence narrow, racemiform; heads sub- 

 sessile. 9' ^^- sessiliflora. 



Leaves except the lowest entire or denticidate; inflorescence open; heads 



peduncled. ^« ,^ » . t- 



Stem-leaves narrowly linear. 10. Af. rubricaulis. 



Stem-leaves oblanceolate. 11. Af. latifolia. 



Bracts linear, with a lanceolate or rhombic green tip, which is usually much shorter 



than the straw-colored lower portion. 

 Leaves cinereous. 



Bracts canescent, scarcely at all viscid or glandular. 



Stem-leaves linear; plant erect. 12. M, canescens. 



Stem-leaves narrowly oblanceolate; plant diffuse. 13. Ai. super Oa. 



Bracts densely viscid or glandular, especially the tips. 



Bracts in but 3 series, not at aU squarrose; the outer wholly greemsh, 



14. M. angustifolia. 



Bracts in 4-7 series with squarrose tips. , , . , j t, ^ 



Stem 1-2 dm. high; upper stem-leaves ample, almost as large and broad 



as the lower ones. 15. Af. commiiia. 



Stem 2-4 dm. high; upper stem-leaves smaller and narrower than the 



lower ones. 

 Heads distinctly peduncled. 



Leaves very thin; stem-leaves entire or nearly so. 



16. Af. leplophylla. 



Leaves thick. , ,. x,, i ^ 



Stem erect, rather simple; stem-leaves Imear-oblanceolate 



or oblanceolate, spinulose-toothed. 17. Af. viscosa. ^ 

 Stem divaricately branched, low; upper leaves small, hnear 

 or some Unear -oblanceolate. 18. A/, pulrerulcnta. 



Heads subsessile, racemosely disposed; stem-leaves linear-oblanceo* 

 late, coarsely toothed. 19. Af. diiancata. 



Leaves glabrous, or glandular-hispid or scabrous, not cinereous. 



Stem puberulent or glabrate, glandular only on the inflorescence. 

 Bracts shghtly if at all squarrose. 



Stem slender, with strongly ascending branches; leaves suhentire. 



20. Af. glabella. 



Stem divaricately branched; lower leaves sharply toothed. 



21. Af. ramosa. 



Bracts strongly reflexed-squarrose. . .t. j i. 



Leaves all, except those of the smaller branches, toothed; achenes stri- 



gose. 22. Af. Selbyi, 



Leaves all entire; achenes glabrous. 23. Af. spectabilis. 



Stem densely glandular-hispid. , . , i.- 



Bracts more or less glandular-pubescent and with squarrose tips. 



24. Af. achonacea. 



Bracts grayish puberulent; tips short, lanceolate, not squarrose. 



2o. M , J* remontit . 



w 



1. M. parviflora A, Gray. Annual; stem 3-5 dm. high, branched, glabrous 

 or nearly so; leaves sparingly glandular, simply pinnatifid; lobes short, linear, 



