[Vol. 2 

 604 ANNALS OF THE MISSOURI BOTANICAL GARDEN 



23, 1901, and in Engl. Bot. Jahrb. 32 : 18, 19. 1902. Lobati 

 Rydb. Bull. Torr. Bot. Club 27 : 169. 1900, in part. 

 Annuals, biennials, or perennials, often forming merely a 



rosette of leaves during the first year; stems erect, 1.5 to 

 10 dm. high from a distinctly annual root or from a rather 

 stout rootstock; leaves once, twice, or thrice pinnately 

 divided; heads numerous; achenes glabrous or pubescent. 

 Sp. 17-29. 



Key to the Species 



A. Annuals or biennials. 



a. Bracts of the involucre usually 13, linear- 



lanceolate, 1 to 2.5 mm. broad 17. S, sanguisorboides. 



b. Bracts of the involucre usually 21, linear 



or linear-lanceolate, 0.5 to 1.5 mm. broad, 

 a. Lateral leaf-segments not abruptly con- 

 tracted into a narrow base. 

 I. Plants of southeastern United States. .18. 8. gldbellus 

 II. Plants of southwestern Texas and 



northern Mexico 19. 8. Grcggii 



)3. Lateral leaf-segments abruptly contracted 



into a narrow 7 base 20. 8. imparipirmatus 



B. Perennials; upright stem from a horizontal, 



ascending or suberect rootstock. 



a. Leaves 2-3-pinnatisect; segments narrow :?/. 8. Millefolium 



b. Leaves once pinnate; segments narrowly obo- 



vate to subreniform. 

 a. Heads numerous, small, 5 to 10 mm. high. 

 I. Involucral bracts usually 21. 



1. Leaves glabrous; achenes hirtellous . 22. 8. tampicanus 



2. Leaves pubescent beneath; achenes 



glabrous 23. 8. hypotrichus 



II. Involucral bracts usually 13. 



1. Lateral leaf -divisions longer than 



broad. 



* Midrib glabrous 2 ; /. 8. Sanguisorbae 



** Midrib floceose-tonientulose. . . . 25. 8. pinnaliscct-us 



2. Lateral leaf-divisions as broad as 



long 26. 8. coahuilensis 



p. Heads fewer and larger, 10 to 14 mm. 



high. 

 I. Leaves pinnately divided nearly to the 



midrib. 



1. Leaf -divisions few, cuneate to reni- 



form 21. 8. levncnsis 



2. Leaf-divisions many, cuneate to 



linear 28. 8. montereyana 



II. Leaves pinnately divided slightly more 



than half-way from margin to 

 midrib 20. 8. zimapanicus 



17. S. sanguisorboides Rydb. Bull. Torr. Bot. Club 27 : 

 170. 1900 ; Wooton & Standley, Contr. XL S. Nat. Herb. 19 : 

 745. 1915. 



