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NORTH AMERICAN FLORA 



[Volume 34 



Annuals; leaves soft, pinnatifid, glabrous, without callous or spinulose tips. 

 Squamellae, at least some of them, aristate. 

 Body of the inner squamellae lanceolate. 



Squamellae 18-20, unequal, all awned and most of them 3-awned. 1. T. polychaeta. 



Squamellae 10, with a long central and short lateral awns, and an 



outer imperfect series of 1-5 small subulate squamellae. 2. T. diffusa. 



Body of the inner squamellae oblong or obovate. 



Squamellae 11-20, the inner 10 each 3 -aristate, but the central awn 

 much longer. 

 Plant low; outer squamellae 1-3, minute. 3. T. tenuifolia. 



Plant tall, 2-5 dm. high; outer squamellae about 10, oblance- 



olate, slightly smaller than the inner. 4. T. anomala. 



Squamellae about 10, all 1 -aristate or some awnless, with two acute 



or obtuse lobes. 5. T. Neaei. 



Squamellae muticous, rather firm. 6. T. aurea. 



Perennials; leaves often spinulose-tipped. 

 Plant not tomentose. 



Involucral bracts practically in one series, all completely coalescent 

 up to the free tips; accessory bracts lanceolate, usually com- 

 paratively conspicuous. 

 Squamellae all 3-aristate. 



Plant erect, 2-3 dm. high, glabrate; leaves entire or with few 



linear-lanceolate divisions. 7. T. Wrightii. 



Plant diffuse, 1-2 dm. high, puberulent; leaves pinnatifid with 



filiform divisions. 8. T. tenuiloba. 



Squamellae unlike, the inner 5 each 1 -aristate, the outer 5 much 

 shorter and obtuse. 

 Involucre hemispheric; leaf -segments short, linear. 9. T. Treculii. 



Involucre turbinate; leaf-segments filiform, long. 10. T. Hartwegii. 



Involucral bracts in two series, united high up but the margins of the 

 outer bracts free and decurrent far down; accessory bracts, if 

 any, subulate and inconspicuous. 

 Leaves glabrous; outer bracts wholly glabrous; ligules broadly 



oval; squamellae all 3-awned. 11. T. aurantiaca. 



Leaves pubescent; bracts puberulent or the outer ones ciliate; 

 ligules oblong; outer squamellae 1 -awned or muticous. 

 Involucre glabrous except the ciliate margins of the outer bracts. 

 All pappus-squamellae awn-tipped although the outer 



shorter. 12. T. Thurberi. 



Outer pappus-squamellae obtuse, much shorter. 



Outer bracts narrowly linear; leaf -segments mostly 5. 

 Leaves spreading, nearly glabrous, with slender 



rather soft segments; stem slender, elongate. 13. T. gracilis. 



Leaves strongly ascending, densely short-pilose, with 



shorter stiff segments. 14. T. pentachaela. 



Outer bracts linear-oblong or lanceolate. 



Margins of the outer bracts decurrent to near the 

 base of the involucre. 

 Leaves green; segments 7—11, very slender. 15. T. myriophylla. 



Leaves villous-canescent; segments mostly 5, short 



and stiff. 16. T. villosula. 



Margins of the outer bracts decurrent only halfway 



down. 17. T. Berlandieri. 



Involucre puberulent or pruinose, the outer bracts scarcely 

 ciliate. 

 Plant neither canescent nor conspicuously depressed. 



Involucre puberulent, nearly hemispheric; leaf -segments 



slender and soft. 18. T. puberula. 



Involucre pruinose-puberulent, campanulate; leaf -seg- 

 ments stiff. 19. T. Pringlei. 

 Plant canescent-pilose, depressed, less than 1 dm. high. 20. T. canescens. 

 Plant tomentose. 



Squamellae distinct, erose, the inner sometimes awned. 21. T. setifolia. 



Squamellae united into a slightly sinuately toothed cup. 22. T. Greggii. 



1. Thymophylla polychaeta (A. Gray) Small, Fl. SE. U. S. 1295. 



1903. 



Hymenatherum polychaelum A. Gray, PI. Wright. 1: 116. 1852. 

 Dyssodia polychaeta B. L. Robinson, Proc. Am. Acad. 49: 508. 1913. 



A glabrous annual; stems 1-2 dm. high, branched from the base, with diffuse ascending 

 branches; leaves opposite and alternate, 3-5 cm. long, pinnatifid into 9-13 filiform divisions, 

 with blunt apex and large glands; peduncles 2-6 cm. long; involucre turbinate-hemispheric, 

 without accessory bracts, 5-6 mm. high, about 8 mm. broad; bracts about 16, oblanceolate, 

 with thin membranous short-acuminate apex, carinate at the base and usually with 2 sub- 



