FLOWERING PLANTS AND FERNS OF ARIZONA 875 



29. Plants not tomentose; pappus of 8 paleae or 

 squamellae (30). 

 30. Heads with fewer than 10 flowers; achenes 

 strongly quadrangular. 



89. Schkuhria. 

 30. Heads with more than 10 flowers; achenes 

 not strongly quadrangular. 



96. Bahia. 



28. Phyllaries not with a scarious colored margin 



and tip (31). 



31. Leaves decurrent; corollas fuscous; pappus 



squamellae about 5, obtuse, much shorter 



than the achene 99. Helexium. 



31. Leaves not decurrent; corollas not fuscous; 

 pappus paleae or squamellae usually more 

 numerous or longer (32) . 



32. Corollas yellow 93. Eriophyllum. 



32. Corollas white, flesh-colored, or purplish 

 (33). 

 33. Plant scapose, with roundish entire or 

 crenate leaves. 



95. Chamaechaenactis. 

 33. Plants leafy-stemmed; leaves not round- 

 ish and entire or subentire (34). 

 34. Pappus paleae with a strong midrib; 

 leaves lanceolate or linear, entire. 



92. Palafoxia. 



34. Pappus paleae nerveless or essentially 



so; leaves, at least in part, toothed 



to pinnatifid 94. Chaexactis, 



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

 none or vestigial; pappus present, of capillary bristles, rarely with addi- 

 tional outer scales. 



Receptacle densely bristly (2). 

 2. Leaf margins neither prickly nor spiny; pappus bristles not united at base nor 



deciduous in a ring 120. Cextattrea. 



2. Leaf margins prickly or spiny; pappus bristles united at base and deciduous 

 in a ring (3) . 

 3. Pappus bristles flatfish, barbellate; leaves blotched with white along the 



veins 119. Silybum. 



3. Pappus bristles slender, plumose; leaves not blotched with white (4). 

 4. Phyllaries comparatively narrow, at least the outer ones spine-tipped. 



117. Cirsium. 

 4. Phyllaries broad (about 1 cm. wide), not spine-tipped __ 118. Cynara. 

 Receptacle naked or chaffy (5). 



5. Phyllaries scarious or hyaline, or in genera Baccharis and Pluchea only 

 partly so (6) . 

 6. Heads unisexual; plants dioecious (7). 



7. Plants large, not tomentose, shrubby, at least at base; heads numerous, 

 in panicles; phyllaries chartaceous, scarious-margined. 



30. Baccharis. 



7. Plants small, tomentose, strictly herbaceous; heads few, in short racemes 



or corymbs, these sometimes panicled, or the heads rarely solitary; 



phyllaries strictly scarious (8). 



8. Heads strictly dioecious; plants low, the basal leaves in a rosette, the 



stem leaves reduced 35. Axtexxaria. 



8. Heads subdioecious, the pistillate ones usually with a few hermaphro- 

 dite flowers in the center; plant usually at least 30 cm. high, 



without a basal rosette 36. Axaphalis. 



6. Heads with the marginal flowers pistillate, the central flowers perfect (9). 

 9. Receptacle chaffv except in the center; plants small, woolly. 



34. FlLAGO. 



9. Receptacle naked (10). 



10. Phyllaries subscarious; corollas purplish; plants not tomentose. 



31. Pi. i ( hi: \. 



