STANDLEY TREES AND SHRUBS OF MEXICO 1433 



A very large, chiefly American genus, most diversified and abundant from 

 Mexico to Argentina. Of little economic importance. Some species are applied 

 in folk medicine. Several have value in horticulture. At least one, with 

 aromatic qualities, is used in flavoring tobacco. 

 A. Receptacle glabrous, flat or nearly so. 



B. Involucre cylindrical, (2-) 3-5 times as long as thick; phyllaries closely 

 imbricated in 3-5 series. Section Cylindrocephala. 



Phyllaries herbaceous-tipped, tending to be squarrose 1. E. sagittatum. 



Phyllaries appressed, not much altered at tip. 



Leaves alternate, subsessile 2. E. pulchellurn. 



Leaves opposite. 



Leaves subsessile by a narrowed cordate base, pinnate-veined. 



3. E. glaberrimum. 

 Leaves petioled, 3 to 5-nerved. 

 Heads 4 to 6-flowered. 



Heads subsessile near tips of panicle branches. 



Stems terete, hollow; leaves tapering from near base. 



4. E. lozanoanum. 

 Stems angled, pithy; leaves broadest near middle. 



5. E. conzattii. 



Heads slender-pediceled, corymbose 44. E. campechense. 



Heads 10 to 40-flowered. 



Heads in ovoid panicles; leaves reticulate-veiny. 

 Heads about 10 to 13-flowered; involucre 2 to 2.6 mm. thick. 



6, E. bertholdii. 

 Heads about 20 to 40-flowered; involucre 4 to 5 mm. thick. 



7. E. ovalifloruin. 



Heads in flattish corymbs; leaves not reticulate. _ 8. E. odoratum. 



BB. Involucre normally campanulate or turbinate, rarely more than twice as 



long as thick; phyllaries less closely imbricated than in the preceding. 



C. Phyllaries conspicuouslj' unequal, in 3 or more series. Section Subim- 



BRICATA. 



D. Heads 1 to 45-flowered; receptacle flat or slightly convex, not noticeably 

 alveolate. 

 Leaves pinnate-veined. 

 Petiole not winged. 

 Leaves opaque. 



Proper tube of corolla much longer than throat. 



9. E. araliaefolium. 

 Proper tube of corolla not equaling throat. 



Leaves 4 times as long as wide, membranaceous, not prom- 

 inently reticulate 10. E. pinabetense. 



Leaves 2 to 3 times as long as wide, subcoriaceous, reticulate. 



Phyllaries rounded at tip 11. E. pittieri. 



Phyllaries pointed at tip 12. E. galeottii. 



Leaves pellucid-reticulate but not pellucid-punctate. 



Leaves lance-oblong; achenes smoothish 13. E. oaxacanum. 



Leaves ovate; achenes gray-villous 14. E. eriocarpum. 



Leaves pellucid-punctate, often also pellucid-reticulate. 

 Veinlets not raised from upper leaf surface. 



Heads sessile or nearly so; leaves drying dark or olivaceous. 

 Leaves membranaceous, obtusish at base. 



15. E. tepicanum. 



