FLOWERING PLANTS AND FERNS OF ARIZONA 877 



28. Pappus bristles more numerous, not caducous '20 . 

 29. Achenes 5-angled or 5-ribbed; corollas white, 

 pink, blue, or purple; leaves often opposite. 55 



4. Eupatoriu.m. 

 29. Achenes not 5-angled or 5-ribbed, or else the corol- 

 las yellow (30). 

 30. Pappus of 5 paleae dissected above into bristles. 



97. Trichoptilium. 

 30. Pappus otherwise (31). 



31. Outer corollas enlarged and palmate; low 

 annual, tomentose below, glandular above. 

 20. Lessixgia. 

 31. Outer corollas not enlarged (32). 



32. Achenes 10-ribbed; involucre usually 



>trongly graduate, the phyllaries striate; 



leaves often opposite; corollas not yellow. 



6. Brickellia. 



32. Achenes not 10-ribbed; phyllaries not 



striate; leaves alternate; corollas nearly 



always yellow (33; . 



33. Phyllaries in a single series of equal 



length, or with a few much shorter 



outer bractlets; style tips truncate. 



116. Sexecio. 

 33. Phyllaries more or less unequal and im- 

 bricate, in more than 1 principal 

 .-eries; style tips not truncate (34 . 

 34. Phyllaries in more or less distinct verti- 

 cal ranks_- 19. Chrysothamxus. 

 34. Phyllaries not in vertical ranks (35). 

 35. Plants woody or else the leaves 

 spinulose-toothed; phyllaries in 

 2 or more graduated series, often 

 closely imbricate. 



18. Aplopappus. 

 35. Plants herbaceous, the leaves not 

 spinulose-toothed; phyllaries 

 usually subequal, scarcely im- 

 bricate 28. Erigerox. 



F. Hermaphrodite flowers with a tubular, regular or nearly regular corolla; rays 

 evident but sometimes small; pappus, of bristles, these mostly capillary, 

 rarely with a few short outer scales. 



1. Rays white, pink, purple, or violet (2). 



2. Leaves and involucre marked with translucent oil glands. _ 103. Dyssodia. 

 2. Leaves and involucre without translucent oil glands (3). 



3. Pappus of 1 or 2 bristlelike awns, these not plumose 84. Laphamia. 



3. Pappus bristles more numerous, or else single and plumose (4). 



4. Ray achenes enveloped by the subtending phyllaries; pappus of the disk 

 achenes of 10 stout hairy bristles, the hairs on their outer side 

 straight, on the inner side entangled into a woolly mass. 80. Layia. 

 4. Ray achenes not enveloped by the subtending phyllaries; pappus other- 

 wise (5). 



5. Ray flowers with pappus none or vestigial 24. Psilactis. 



5. Ray flowers with evident pappus (6). 



0. Plants dwarf hispid-hirsute winter annuals; upper leaves closely 

 subtending the heads; pappus of a single plumose bristle and a 

 scarious cup, or of numerous unequal bristles or narrow paleae. 



25. Moxoptilox. 

 6. Plants otherwise in habit, or in the pappus (7). 



7. Style tips lanceolate or subulate, acute or acuminate; phyllaries 

 usually strongly graduated, often partly herbaceous: rays 



mostly relatively broad 27. Aster. 



7. Style tips deltoid, obtuse or rounded; phyllaries usually equal 

 or little graduated; rays mostly very narrow. 28. Erigerox. 



' Brickellia florihnnda, which might also run down To this point in the key. may be distinguished from 

 any native species of Eupatorium by its combination of rather large heads (9 to 12 mm. high) and strongly 

 graduated involucre of obtuse or obtusish phyllaries. 



