THISTLE FAMILY 897 



Stem-leaves not cordate-clasping. 



Stems rather simple, with a few large heads ; disks about 1 cm. broad 



or more. XII. ASPEBI. 



Stems much branched, leafy, with numerous small heads; disk 6-9 



mm. wide. 



Stems strigose or sparingly hirsute except at the base, or glabrous; 

 pappus-bristles of the ray-flowers usually lacking; annuals. 



XIII. RAMOSI. 

 Stems and leaves densely short-pubescent with spreading hairs; 



pappus-bristles of the ray-flowers present. 

 Annuals; pappus scant and simple. XIV. BELLIDIASTRA. 



Biennials (rarely perennials) ; pappus double, the outer of short 



subulate squamellae. XV. DIVERGENTES. 



Plants at first with a scapiform naked peduncle, later producing runner-like 



branches. XVI. FLAGELLARES. 



Bracts of the involucre in 34 series, more or less imbricate, thickened on the back, the 



outer usually successively shorter; perennials with cespitose caudices. 

 Rays bluish, purplish, or white. 



Achenes terete or nearly so, several-nerved. XVII. CANT. 



Achenes flattened or quadrangular, 2-4-nerved. 



Leaves more or less distinctly triple- nerved. XVIII. CAESPITOSI. 



Leaves not triple-nerved. 



Plants low, 2 dm. or less high; basal leaf-blades from broadly oval to nar- 

 rowly linear-oblanceolate ; heads solitary to few. 



Basal leaf-blades broadly oval or obovate. XIX. ASPERUGINEI. 



Leaves narrowly linear-oblanceolate. 



Involucres glandular. XX. ARENARIOIDES. 



Involucres hirsute or strigose. XXI. LAETEVIRENTES. 



Plant taller, 3-4 dm. high; leaves filiform or narrowly linear. 



Leaves narrowly linear or linear-oblanceolate; achenes quadrangular, 



4-nerved. XXII. TETRAPLEURI. 



Leaves filiform; achenes flat, 2-nerved. XXIII. FILIFOLII. 



Rays yellow or ochroleucous. XXIV. LUTEI. 



I. ACRES. 



Bracts of the involucre linear, abruptly acute, never glandular; inner rayless pistillate 



flowers rare; inflorescence strictly racemiform, with almost erect branches. 

 Low, 1-2 dm. high, usually branched at the base; stem-leaves sessile; peduncles short, 



not exceeding the subtending leaves. 1. E. minor. 



Taller, 3-6 dm. high, simple; lower stem-leaves petioled; basal leaves oblanceolate; 



peduncles elongate. 2. E. lonchophyllus. 



Bracts of the involucre linear-subulate, long-attenuate, and except in E., elatus more 

 or less glandular-puberulent ; inflorescence inclined to be corymbiform or panicu- 

 late, branches ascending. 



Plant tall, 3-8 dm. high, apparently only biennial; heads numerous, corymbose. 

 Bracts glandular-puberulent, rarely with a few hairs. 



Base of the involucre merely glandular-puberulent; whole plant glabrous or 

 the margins of the leaves sparingly ciliate; stem-leaves lanceolate. 



3. E. politus. 



Base of the involucre sparingly hirsute; leaves hairy, at least on the margins 

 and veins beneath; stem-leaves Linear or lindar-oblanceolate. 



4. E. droebachensis. 

 Bracts hirsute or both hirsute and glandular-puberulent. 



Bracts both glandular-puberulent and hirsute; leaves more or less hairy. 



5. E. yellowstonensis. 

 Bracts not glandular; leaves glabrous except the ciliate margins. 



6. E. elatus. 

 Plant low, 1-3 dm. high, perennial; heads few or solitary. 



Involucres not black-hairy. 



Involucres glandular and hirsute. 7. E. jucundus. 



Involucres villous, not glandular. 8. E. alpinus. 



Involucre black-hairy. 9. E. unalaschkensis. 



II. UNIFLORI. 

 Ligules purple or white. 



Ligules 0.5 mm. or less wide, erect; plant usually less than 1 dm. high; leaves and 



stem decidedly villous. 9. E. unalaschkensis. 



Ligules 1-1.5 mm. wide, spreading; plant about 1 dm. high; basal leaves glabrate; 



lower part of the stem strigose or glabrate. 



Involucres and peduncles with black-purple hairs. 10. E. melanocephalus. 



Involucres and peduncles white-hairy. 



Basal leaves sparingly hairy or glabrate. 



Basal leaves spatulate, obtuse. 11. E. simplex. 



Basal leaves narrowly linear-lanceolate. 92. E. Scribneri. 



Basal leaves densely villous. 



Stem 1-2 dm. high, leafy; basal leaves oblanceolate, often acutish. 



12. E. grandiflorus. 

 Stem 5-6 cm. high, scapiform ; basal leaves cuneate-spatulate, often 3- 



toothed. 13. E. lanatus. 



Ligules yellow. 14. E. aureus. 



