44 NORTH AMERICAN FLORA [Volume 34 



Disk-flowers not subtended by membranous paleae ; heads discoid, 



except in one species. 36. Hymenopappus. 



Disk-flowers subtended by membranous paleae, which partly 



enclose the fruit; heads radiate. 37. Leucampyx. 



Disk-corollas with cylindro-campanulate throat and erect lobes; bracts 

 oblong; squamellae narrowly linear-lanceolate, with the midrib 



excurrent into a barbellate awn ; heads radiate. 38. HymENOTHRIX. 



Disk-corollas deeply cleft into linear-oblong lobes at least three times as 

 long as the funnelform throat. 

 Principal bracts oblong, subtended by linear smaller ones; corollas 



cleft nearly to the tube; anthers wholly exserted. 39. TrichymEnia. 



Bracts subequal, obovate; corollas of the disk-flowers deeply cleft but 



with a distinct funnelform throat; anthers partly exserted. 40. FloresTINA. 



34. TETRACARPUM Moench, Meth. Suppl. 240. 1802. 



Schkuhria Roth, Catal. 1: 116. 1797. Not Schkuhria Moench, 1794. 



Mieria Llave; Llave & Lex. Nov. Veg. Descr. 2: 9. 1825. 



Achyropappus Link & Otto. Ic. PI. Rar. pi. 30. 1829. Not Achyropappus H. B. K. 1820. 



Hopkirkia DC. Prodr. 5: 660. 1836. Not Hopkirkia Spreng. 1818. 



Slender, paniculately branched annuals. Leaves alternate or the lower opposite, pin- 

 nately divided into linear or filiform divisions, conspicuously impressed-punctate. Heads 

 radiate or discoid. Involucre turbinate or obpyramidal; bracts 4 or 5, rarely 6, more or less 

 scarious, colored and petaloid at the apex, keeled on the back, often subtended by 1-3 bract- 

 lets at the base. Receptacle small. Ray-flowers 1-6, with ascending or spreading, sometimes 

 obsolete, ligules, or wanting. Disk-flowers usually few; tube glandular, shorter than the 

 campanulate throat; lobes 5, rather short. Achenes narrowly obpyramidal, 4- angled, hispidu- 

 lous on the angles, especially below. Pappus of 8 scarious squamellae with callous-thickened 

 bases or a prominent midrib, those on the angles sometimes larger. 



Type species, Tetracarpum pinnatum Moench. 



Ray-flowers 1 or 2, or wanting, with short ascending ligules. 

 Squamellae obtuse. 



Squamellae subequal, 1.5 mm. long. 1. T. Wrightii. 



Squamellae unequal, the longer less than 1 mm. long. 2. T. Pringlei. 



Squamellae acute, usually awn-tipped. 

 Squamellae equal. 



Ligules 1 mm. long or less, not longer than the disk -flowers. 3. T. anthemoideum. 



Ligules fully 2 mm. long, much exceeding the disk -flowers. 4. T. guatemalense. 



Squamellae unequal, those at the angles much longer. 



Ligules 1 mm. long or less, scarcely exceeding the disk -flowers. 



Achenes short-hairy on the angles. 5. T. virgatum.^ 



Achenes long-hairy on the angles. 6. T. Wislizeni. 



Ligules 2-3 mm. long, much exceeding the disk -flowers. 7. T. flavum. 



Ray-flowers 3-6, with more conspicuous spreading ligules. 8. T. schkuhrioides. 



1 . Tetracarpum Wrightii (A. Gray) Rydberg. 



Schkuhria Wrightii A. Gray, PI. Wright. 2: 95. 1853. 



A slender annual; stem erect, angled, striate, glandular-puberulent, 2-3 dm. high, with 



ascending branches; leaves alternate, pinnately dissected into filiform divisions, 2-4 cm. long, 



sparingly puberulent and conspicuously impressed-punctate; peduncles 1-2 cm. long; involucre 



obconic, 4-5 mm. long; bracts glabrous, obovate, conspicuously punctate, with more or less 



purple-tinged scarious margins and apex; ligule one or wanting, ascending, 1 mm. long; 



disk-flowers 3-5; achenes 3 mm. long, densely long-pubescent on the edges, striate on the 



faces; squamellae 8, obovate, similar, rounded at the apex, purple-striate. 



Type locality: "On the Sonorita near Deserted Rancho," Sonora. 

 Distribution: Chihuahua, New Mexico, Arizona, and Sonora. 



2. Tetracarpum Pringlei (S. Wats.) Rydberg. 



Schkuhria Pringlei S. Wats. Proc. Am. Acad. 23: 278. 1888. 



A slender annual; stem 3-5 dm. high, somewhat angled, sparingly puberulent and slightly 

 glandular; leaves alternate, pinnately 3-7-divided into narrowly linear divisions or the upper 

 entire, distinctly punctate but nearly glabrous; peduncles 1-2 cm. long; involucre obconic, 

 5 mm. high, 3 mm. broad; bracts obovate, punctate, yellowish-green with purplish tinged mar- 

 gins; disk-flowers 7-9; corolla yellow, nearly 2 mm. long; achenes elongate-obpyramidal, 4 mm. 



