STANDLEY TREES AND SHRUBS OF MEXICO 1499 



1. Erigeron socorrensis T. S. Brandeg. Erythea 7: 4. 1899. 



Socorro and San Benedicto Islands, Baja California; type from Socorro 

 Island. 



Frutescent, hirsutulous; leaves crowded, linear-oblanceolate to obovate, 

 2.5 to 7 cm. long, 3 to 15 mm. wide, entire, crenate, serrate, or few-lobed, thickish, 

 narrowed into a petioliform base; heads tiny, white, in terminal panicles; in- 

 volucre hirsutulous, slightly graduate. 



2. Erigeron exilis A. Gray in S. Wats. Proc. Amer. Acad. 22: 422. 1887. 

 Jalisco; type from Rio Blanco. 



Suffruticulose, slender, about 25 cm. high, granular-puberulous, at least above, 

 and somewhat hirsute or strigillose; leaves linear-oblanceolate, 1 to 2.5 cm. 

 long, 1 to 2.5 mm. wide, acute, entire; heads white, 1.5 cm. wide, sohtary at tips 

 of branchlets; phyllaries somewhat graduate, linear-lanceolate, acuminate, the 

 inner usually purplish above and subscarious. 



3. Erigeron calcicola Greenm. Proc. Amer. Acad. 41: 256. 1905. 

 Coahuila to Hidalgo; type from Tula, Hidalgo. 



Suffruticulose, 15 to 30 cm. high; leaves oblanceolate to spatulate-linear, 2.5 

 cm. long or less, 1 to 5 mm. wide, entire or the lower few-toothed; heads long- 

 pedunculate, 1.5 to 2 cm. wide; phyllaries hirsutulous; rays white or purple- 

 tinged; pappus double. 



4. Erigeron ervendbergii A. Gray, Proc. Amer. Acad. 8: 650. 1873. 



San Luis Potosi to Puebla and Veracruz; type from Wartenberg, Veracruz. 



Suffruticulose, decumbent at base, with several slender stems, about 30 cm. 

 high; leaves linear to oblanceolate, usually 2.5 cm. long or less, the lower some- 

 times 6 cm. long, coarsely few-toothed, narrowed into a slender petiole; heads 

 long-peduncled, 2 cm. wide; involucre subequal; rays purplish-tinged; pappus 

 double. 

 6. Erigeron karvinskianus DC. Prodr. 5: 285. 1836. 



Erigeron mucronatus DC. Prodr. 5: 285. 1836. 



Erigeron trilobus Sonder, Hamb. Gart. Zeit. 12: 78. 1856, excluding synonym. 



Erigeron karvinskianus mucronatus Hieron. Bot. Jahrb. Engler 28: 585. 1901. 



Vittadinia triloba Auct., not DC. 



San Luis Potosi to Chiapas. Guatemala; South America. 



Suffruticulose, slender, decumbent, 60 cm. long or less; lower leaves usually 

 cuneate or obovate, few-toothed or lobed, 3 cm. long or less, mucronate, the upper 

 or sometimes all linear-lanceolate, entire; heads long-peduncled, 2 cm. wide; 

 involucre subequal, the linear acuminate phyllaries usually sparsely strigose; 

 rays white or purplish-tinged; pappus double. 



DOUBTFUL SPECIES. 



Erigeron diplopappoides Schauer, Linnaea 19: 722. 1847. 



29. BACCHARIS L. Sp. PI. 860. 1753. 

 Shrubs, rarely only suffrutescent, dioecious; leaves alternate, entire or toothed; 

 heads small or medium, discoid, whitish, cj-mose or panicled, rarely .subsolitary ; 

 involucre graduate, the phyllaries dry, sometimes with green midrib, narrowly 

 scarious-margined; receptacle naked, very rarely paleaceous; pistillate heads 

 with tubular-filiform corollas; staminate heads with the flowers hermaphrodite 

 but sterile, with tubular 5-toothed corollas; achenes small, 5 to 10-nerved; 

 pistillate pappus of soft capillary bristles, 1 to several-seriate, persistent; stamin- 

 ate pappus stiffer, the bristles often somewhat dilated above. — The descriptions 

 of achenes and pappus in the following treatment refer only to the pistillate heads. 



