ROBINSON AND GREENMAN. — TRIXIS. 7 



bracts and 5 to 10 equal erect liuear-oblong scales: corollas yellow, 

 strongly bilabiate, the upper erect lip 2-cleft, the lower spreading, 

 3-toothed or subentire : anthers sagittate and bicaudate at the base : 

 achenes cylindrical or slightly flask-siiaped, slender, finely papillose, the 

 summit more or less expanded into a circular disk bearing copious simple 

 roughish white or tawny pappus-bristles. — Hist. Jamaic. 312 (1756); 

 Lag. Amen. Nat. i. 35 ; La Llav. & Lex. Nov. Veg. Desc. fasc. 1, 27 ; 

 Sprang. Syst. iii. 501; D. Don, Trans. Linn. Soc. xvi, 186, 297; DC. 

 Prodr. vii. pt. 1, 67 ; Benth. & Hook. f. Gen. ii. 501 ; Hemsl. Biol. 

 Cent.- Am. Bot. ii. 257; Hoflfra. in Engl. & Prantl, Nat. Pflanzenf. 

 iv. Abt. 5, 350; Hook. f. & Jacks. Ind. Kew. ii. 1130, which see for 

 generic synonymy. Perdicium^ L. PI. Afr. Rar. 22 (1762), in part. 

 About 35 species, ranging from Arizona to Brazil and Chili. 



§ 1. Inflorescence an elongated conical thyrsus : herbaceous. 



1. T. raichuacana, La Llav. & Lex. Viscid-resinous and with a 

 heavy odor; root fibrous, yellowish; stem simple, tomentose, 1 dm. 

 high, erect : leaves sessile, punctate, villous below, the fioral gradually 

 reduced : heads borne in a large conic-oblong thyrsus ; outer bracts of 

 the involucre 5, ample, ovate, the inner involucre prismatic, of 8 erect 

 scales. — Nov. Veg. Desc. fasc. 1, 28 (1824) ; DC. Prodr. vii. pt. I, 68 ; 

 Hemsl. Biol. Cent.-Am. Bot. ii. 258. — Michoacan: near Valliso- 

 letum, flowering in January, Lexarza. If the above (compiled) descrip- 

 tion is correct, this is a marked species, not yet rediscovered. 



§ 2. Inflorescence corymbose-paniculate : shrubs or undershrubs. 

 * Leaves sessile by a clasping shortly decurrent base. 



2. T. decurrens, DC. Stems several, sparingly branched toward 

 the summit: leaves crowded, ovate-lanceolate, acutely acuminate, entire: 

 heads terminal, subsolitary ; outer involucre of 5 ovate-lanceolate bracts, 

 the inner of 8 scales: corollas yellow. — Prodr. vii. pt. 1, 68 (1838), 

 whence the foregoing description ; Hemsl. Biol. Cent.-Am. Bot. ii. 

 258 ; A. DC. Caiques des Dess. t. 515. Perdicium decurrens, Sesse & 

 MociSo, ace. to DC. 1. c. (1838), & Pi. Nov. Hisp. ed. 2, 130.— 

 MoRELOS : Ayacapixtla, flowering in November, Sesse ^ Mocino. 



* * Stem provided at least at some stages of its development with broad and 



conspicuous herbaceous wings. 

 -1- Outer bracts of the involucre lanceolate, much shorter than tlie inner; tlie 



latter glandular. 



3. T. mexicana, La Llav. & Lex. A meter or more high : -leaves 

 lanceolate, 5 to 13 cm. long, 1 to 4 cm. broad, acuminate, acute, entire 



