2(1). Leaves with numerous marginal setae ( 3 ) 



2. Leaves with no (or very few) marginal setae 1. E. sparganophyllum. 



3(2). Leaves 10-30 mm. broad, the marginal setae usually solitary; bracts ovate- 

 lanceolate 2. E. yuccifolium var. yuccifolium. 



3. Leaves 5-10 mm. broad, the marginal setae usually in groups of 2 to 4; bracts 



linear-lanceolate 3. E. yuccifolium var. synchaetum. 



4(1). Cauline leaves conspicuously spinulose-pungent; bracts mostly broad, vari- 

 ously spinose-toothed, rarely entire, pungent (5) 



4. Cauline leaves entire to pinnatifid, not spinulose-pungent; bracts very narrow, 



sometimes pungent-tipped, entire or occasionally with 3 to 5 spiny 

 teeth (7) 



5(4). Inflorescence a single head (rarely more); basal leaves on long petioles 



4. E. phyteumae. 



5. Inflorescence cymosely or paniculately branched (6) 



6(5). Bracts bicolored, green or bluish beneath, yellow-white above 



5. E. heterophyllum. 



6. Bracts greenish above and below, not bicolored 6. E. Hookeri. 



7(4). Plant erect; lower bractlets tricuspidate; basal leaves usually cordate 



7. E. integrifolium. 



7. Plants prostrate to ascending; bractlets entire; basal leaves not cordate (8) 



8(7). Heads in a terminal branched inflorescence, subsessile, many-flowered; 

 bractlets exceeding the fruit 8. E. nasturtiifolium. 



8. Heads solitary, on filiform peduncles, few-flowered; bractlets shorter than the 



fruit 9. E. prostratum. 



1. Eryngium sparganophyllum Hemsl. 



Slender caulescent glabrous perennials, 4-12 dm. high; stems solitary to several, 

 erect; basal leaves numerous, Hnear to linear-lanceolate, 1-9 dm. long, 5-15 mm. 

 wide, broadest at base, attenuate at apex, entire or obsoletely spinulose-dentate 

 with teeth 2 mm. long or less, axillary spines absent, venation parallel; cauline 

 leaves few and reduced; inflorescence branching; heads ovoid or ovoid-oblong, 

 15-25 mm. long, 10-15 mm. broad; bracts 8 to 12, much shorter than heads; 

 bractlets 5 mm. long, slightly exceeding fruit; coma wanting; fruit ovoid, 3-4 mm. 

 long. 



Wet seeps and marshy ground, Ariz. (Pima Co.), e. into N.M. (Grant Co.), s. 

 into Mex. 



2. Eryngium yuccifolium Michx. var. yuccifolium. Rattlesnake-master, button 



SNAKE-ROOT. 



Plants stout, glabrous, 3-18 dm. high, perennial from a fascicle of tuberous 

 woody roots; stems slender, solitary, branching above; basal leaves rigid, broadly 

 linear, to 10 dm. long, 1-3 cm. wide, acute, remotely bristly with solitary (or 

 occasionally 2 or more) bristles, the venation parallel; sheaths short; cauline leaves 

 like the basal, reduced above; inflorescence cymosely branched, the pedunculate 

 heads large, the flowers numerous; heads globose-ovoid, 1-2.5 cm. in diameter; 

 bracts 6 to 10, spreading-ascending, ovate-lanceolate, to 15 mm. long, cuspidate, 

 mostly entire, shorter than the heads; bractlets like the bracts, entire or minutely 

 serrulate, exceeding the fruit; coma wanting; sepals ovate, obtuse, mucronulate; 

 styles exceeding the sepals; fruit oblong, 4—8 mm. long, the flattened scales of the 

 angles lanceolate, 1.5-3 mm. long, those of the dorsal surfaces reduced or obsolete. 



1254 



