814 OPUNTIACEAE 



or somewhat flattened, straight: flowers mainly purple, 5-7.5 cm. long. \E. "bicolor 

 var. Schottii Engelm.] 



On limestone hills, southern Texas and adjacent Mexico. 



2. Echinocactus setispinus Engelm. Stems subglobose, solitary, 5-9.5 cm. in 

 diameter, the ribs 13, somewhat oblique, more or less undulate or even slightly inter- 

 rupted: spines various; radials 14-16, bristle-like, 1-2 cm. long, the upper longer than 

 the rest and like the lower, yellowish brown, the lateral ones white; centrals 1-3, 

 darker than the radials, 24-32 mm. long, bristle-like: flowers 4-7 cm. long, yellow 

 and scarlet within: fruits subglobose, about 8 mm. in diameter, red: seeds obliquely 

 globose-ovoid, 1.2-1.6 mm. long, tuberculate. 



In mesquite thickets and dry soil, from the valley of the Brazos, Texas, southward 

 into Mexico. 



3. Echinocactus Tex6nsis Hoepf . Stems depressed or rarely subglobose, 2-3 

 dm. broad, seldom over 15 cm. high, solitary, simple, the ribs 13-27, usually 21, 

 wavy: spines reddish, stout, flattened, clustered; radials 6-7, straight or slightly 

 curved, spreading, 12-20 mm. long, rarely longer or shorter; central one surpassing 

 the outer, commonly 4-5 mm. broad or slightly broader, straight or slighty curved: 

 flowers orange and scarlet below to white above, about 5 cm. long: fruits scarlet, 

 subglobose, 16-18' mm. in diameter: seeds reniform, 2.4-2.8 mm. long, black, smooth 

 and shining or minutely pitted. 



On prairies, south-central Texas and adjacent -Mexico. 



4. Echinocactus Wrightii (Engelm.) Small. Stems ovoid or oval, 7.5-15 cm. 

 high, 5-8.5 cm. thick, the ribs 13, with interrupting tubercles grooved to the base: 

 spines various; radials about 8, 3-5 cm. long, the upper straight, flattened, the 3 

 lower hooked, terete, darker than the upper; central solitary, 5-15 cm. long, erect, 

 straw-colored with a dark tip, zigzag, hooked: flowers dark purple, 2.5-3.5 cm. long: 

 fruits reddish, 1.5-2.5 cm. long, fleshy: seeds flattened, curved, 1.4-1.6 mm. long, 

 tuberculate, keeled along the back. [E. uncinatus var.? Wrightii Engelm.] 



In dry soil, along the Rio Grande, Texas and adjacent Mexico. 



5. Echinocactus Muhlenpfordtii Fen. Stems globose-ovoid to oblong-cylindric, 

 10-20 cm. high, the ribs often 13, more or less oblique: spines various; radials 10-12, 

 subulate, bristle-like, 12-32 mm. long, the upper longer than the lower; central 

 solitary, firm, 25-35 mm. long, hooked: flowers 5-7 cm. long, yellow and scarlet 

 within: fruits globular, red, 8"-10> mm. long. 



In sandy soil, Texas and adjacent Mexico. 



3. ECHINOCEREUS Engelm. 



Plants ovoid, cylindric or columnar, ribbed and angled, or tubercled with numer- 

 ous spine-bearing areolae. Flowers arising from areolae situated just above fully 

 developed spine-bearing areolae. Seeds tuberculate. Fruits fleshy. 



Radial spines 20-30, pectinate. 1. E. caespitosus. 



Radial spines 4-12, not pectinate. 

 Joints over 2 cm. thick. 



Central spines usually 2-4. 2. E. dubius. 



Central spines always solitary. 



Longer radial spines over 1 cm. long: stems erect. 3. E. Fendleri. 



Longer radial spines less than 1 cm. long: stems procumbent. 4. E. Berlandieri. 



Joints less than 2 cm. thick. 5. E. procumbent 



1. Echinocereus caespitosus Engelm. & Gray. Stems ovoid, globose or cylin- 

 dric-ovoid, 2.5-5 or rarely nearly 15 cm. high, solitary or commonly 6-12 stems to- 

 gether, the ribs 12-13, straight; tubercles confluent: areolae close together: spines 

 numerous, white or rarely pink or brown; outer 20-30 straight or slightly recurved, 

 pectinate, the lateral ones 4-8 mm. long, the upper and lower shorter; central spines 

 wanting or rarely 1 or 2 but very short : flowers rose-purple, 5-7.5 cm. long and nearly 

 as broad: hypanthium furnished with cushions bearing brown or black bristles: 

 fruits ovoid, green, 18-20 mm. long: seeds black, 1.2-1.4 mm. long, tuberculate. 



On prairies, Kansas to Texas and adjacent Mexico. A variety with reddish or chestnut- 

 brown spines is E. caespitosus castaneus Engelm. 



2. Echinocereus dubius (Engelm.) Small. Stems ovoid-cylindric, 12-20 cm. 

 high, pale green, rather flabby, usually tufted, the ribs 7-9, with tubercles: areolae 

 remote: spines white, somewhat translucent; lateral ones radiant, 12-30 mm. long, 

 terete or slightly angled, upper ones reduced or obsolete; central spines 1-4, straight 

 or curved, 3.5-7.5 cm. long, angled: flowers pale purple, 6 cm. long and broad: fruits 

 green or purplish, 2.5-3.5 cm. long, spiny: seeds globose-ovoid, 1.2-1.4 mm. long, 

 tuberculate. [Cereus dubius Engelm.] 



In river bottoms, southern Texas and adjacent Mexico. 



