FLOWERING PLANTS AND FERNS OF ARIZONA 59*3 



rather persistent; fruit spiny with large and readily detachable spine 

 clusters, thin-fleshed, juicy, edible; seeds black, tuberculate, the 

 tubercles more or less confluent. 



Key to the species 



1. Flowers scarlet or crimson (2). 



2. Plant with few stems, these stout, 20 to 50 cm. long; central spines 3 or 4, 

 stout, straight, subulate, often angled, ashy gray or darkened. 



1. E. POLYACAXTHUS. 



2. Plant strongly proliferous; stems seldom more than 20 cm. long (3). 



3. Stems seldom more than 50; spines straight or nearly so. never flexuous, 

 not or scarcely angled, often clear yellow; central spines 1 to 4, acicular. 



2. E. coccixeus. 



3. Stems often very numerous (500 or more) in large hemispheric mounds; 



spines curved or even flexuous, angled, ashy gray; central spine solitary. 



3. E. MOJAVENSIS. 

 1. Flowers purple (4). 



4. Areoles narrowly elliptic; radial spines closely appressed and pectinate, not 



more than 12 mm. long, red or pink 4. E. rigidissimus. 



4. Areoles oblong to circular: radial spines not pectinate; central spines never 

 wanting (5). 

 5. Central spines 2 to 6 or more, all well developed, more or less curved or 

 twisted, the lower ones derlexed, commonly flattened and angled 

 toward the base; stems stout, up to 50 cm. long; ribs 11 to 18. 



6. E. EXGELMAXXII. 



5. Central spines solitary, terete, often accompanied by shorter superposed 

 accessory centrals (6). 

 6. Central spine curved toward the base, derlexed; spines translucent, 

 straw colored, monochromatic; accessory centrals 1 to 4, or wanting; 



stems stout, up to 50 cm. long; ribs 13 to 16 5. E. ledixgii. 



6. Central spine not curved near the base; spines commonly opaque (7). 

 7. Ribs 12 to 22, usually 14 to 17; principal central spine porrect or 

 deflexed, reddish, white, or rarely straw-colored and translucent; 

 1 or 2 accessory centrals on at least some of the areoles. 



7. E. BOYCE-THOMPSOXI. 



7. Ribs 8 to 13, usually not more than 10; central spines dark brown or 

 ashy gray (8). 

 8. Central spine curved and, except in age, strongly ascending, flexible, 

 2.5 to 4.5 cm. long; accessory centrals wanting; radials straight 

 or curved; stem rarely more than 15 cm. long, flaccid. 



8. E. FEXDLERI. 



8. Central spine straight, porrect; accessory centrals usually present 

 on some of the areoles; stern rarelv less than 15 cm. long, firm 

 (9). 

 9. Spines 1 to 2.5 cm. long, stout, rigid; stems 1 to 5 in number, 8 



to 25 cm. long 9. E. rectispixus. 



9. Spines 2.5 to 6 cm. long, flexible; stems as many as 15, 25 to 45 

 cm. long 10. E. ROEUSTrs. 



1. Echinocereus polyacanthus Engelm. in Wisliz., Mem. North. Mex. 



104. 1848. 



Echinocereus arizonicus Orcutt, Cactography 3: 3. 1926. 



Graham, Pinal, Cochise, and Pima Counties, mountains, 4,000 to 

 6,000 feet, April and May. New Mexico, Arizona, and Mexico. 



The flowers are usually larger than those of the 2 following species, 

 attaining a length of 6 or 7 cm. E. polyacanthus (pi. 22) is understood 

 by the writers to embrace a variety of forms, including E. arizonicus, 

 which has short wool in the axils of the hypanthium scales. The type 

 locality of E. arizonicus is the Pinal Mountains, Pinal County. 



A. A. Nichol has verbally reported having collected living plants of E. triglo- 



chidiatus Engelm. near Fort Defiance, Apache County, in 1035. This species, 

 which occurs in Colorado, Utah, western Texas, and New Mexico, has scarlet 



