STANDLEY TREES AND SHRUBS OF MEXICO 1607 



Involucre ecalyculate or with very short and minute outermost phyllaries. 

 Leaves acerose, entire; pappus paleae all dissected into 3 to 5 bristles. 



9. D. acerosa. 

 Leaves pinnatisect; pappus paleae with 1 to 3 awns or awnless. 

 Plants canescent-tomentose. 



Pappus paleae distinct 16. D. setifolia. 



Pappus paleae united into a cup 17. D. greggii. 



Plants glabrous to densely puberulous or cinereous-pilosulous. 

 Involucre densely puberulent or pruinose. 



Principal phyllaries united essentially up to the short free tips, the 

 margins of the outer principal ones not free. 

 Heads larger; involucre 6 mm. high, 5 to 7 mm. wide. 



10. D. treculii. 

 Heads smaller; involucre 3.5 to 4.5 mm. high, 2 to 5 mm. wide. 



11. D. hartwegii. 



Principal phyllaries less completely united, the outer ones with 



margins free for half their length or more. .12. D. pentachaeta. 



Involucre glabrous except for the ciliate margins of the phyllaries. 



Principal phyllaries united essentiallj^ to the short free tips, the 



margins of the outer ones not free; accessory phyllaries (forming 



the caly cuius) conspicuous 10. D. treculii. 



Principal phyllaries less completely united, the outer with margins 

 free for half their length or more. 



Pappus paleae all split into 3 to 5 awns 15. D. aurantiaca. 



Pappus paleae 1-awned or awnless. 



Outer pappus paleae obtuse or acute, not ^istate. 



13. D. berlandieri. 

 Pappus paleae all aristate 14. D. thurberi. 



1. Dyssodia oazacana Greenm. Field Mus. Bot. 2: 273. 1907. 

 Gymnolaena oaxacana Rydh. N. Amer. Fl. 34: 160. 1915. 

 Oaxaca; type from Almoloyas. 



Shrub 1.3 to 2 meters high, slightly pubescent; leaves opposite, the blades 

 elliptic-ovate, 1 to 4 cm. long, 4 to 11 mm. wide, acute, serrate, narrowed to a 

 short petioliform base; heads solitary or few, about 1.8 cm. high; involucre 

 about 1.4 cm. high, the phyllaries united nearly to apex; pappus paleae dissected 

 into numerous bristles. 



2. Dyssodia serratifolia DC. Prodr. 5: 641. 1836. 



Hyrnenatherum serratifolium Hemsl. Biol. Centr. Amer. Bot. 2: 221. 1881. 



Dyssodia sessilifolia A. Gray, Proc. Amer. Acad. 19: 37. 1883. 



Gymnolaena serratifolia Rydb. N. Amer. Fl. 34: 161. 1915. 



Oaxaca; type from Atitla. 



Shrubby, essentially glabrous; leaves chiefly opposite, the blades 5 to 8 cm. 

 long, acute, serrate, densely glandular-punctate; heads cymose, about 1.3 cm. 

 wide; involucre 1 cm. high. 



3. Dyssodia integrifolia A. Gray, Proc. Amer. Acad. 19: 37. 18S3. 

 Grjmnolaena integrifolia Rydb. N. Amer. Fl. 34: 161. 1915. 

 Puebla to Chiapas; type from Chiapas. 



Similar to D. serratifolia; leaf blades 2.2 to 5 cm. long, acuminate, serrulate; 

 heads mostly solitary; involucre 1.3 to 1.7 cm. high. 



4. Dyssodia speciosa A. Gray, Proc. Amer. Acad. 5: 163. 1861. 

 Lehetina speciosa A. Nels. Bot. Gaz. 47: 435. 1909. 

 Clomenocoma speciosa Rydb. N. Amer. Fl. 34: 165. 1915. 

 Southern Baja California; type from Cape San Lucas. 



