OPUNTIACEAE 813 



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. 

 B. Joints less than 2 cm. thick. 



Radial spines 4-6 : stems more or less angled : flowers over 7 cm. broad. 5. E. procumbens. 



Radial spines 9-12 : stems terete : flowers less than 6 cm. broad. 6. E. Poselgeri. 



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

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

 nished with cushions bearing brown or black bristles : fruit 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 castdneus Engelm. 



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

 pale green, ratherflabby, 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 : fruit 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. 



3. Echiiiocereua F6ndleri (Engelm.) Small. Stems ovoid to cylindric-ovoid, 7.5-20 

 cm. high, 5-7.5 cm. thick, simple or branched at the base, the branches tufted, the ribs 9-12, 

 sometimes oblique, tuberculate : areolae less than 1.5 cm. distant : spines short ; radials 

 5-10, straight or sometimes curved, variable, lowest one 12-25 mm. long, shorter than the 

 rest, angled, the next 2 about as long or longer, more or less blackish ; succeeding ones shorter 

 and weaker, 6-14 mm. long, occasionally accompanied by a spine at the top of the areolae 

 surpassing all the rest in length ; central spine solitary, nearly terete, 2.5-5 cm. long, 

 reddish black, upcurved from a bulb like-base : flowers 6-8.5 cm. broad, deep violet 

 purple : fruit 2.5 cm. long, purplish green, edible : seeds less than 1.5 mm. long. [Cereus 

 Fendleri Engelm. ] 



In dry soil, Utah to Texas, Arizona and northern Mexico. 



4. Echinocereus Berlandieri (Engelm. ) Small. Stems jointed, spreading, decumbent, 

 much -branched, the joints nearly terete, 3.5-15 cm. long, 2-2.5 cm. thick, their ribs 5-6, 

 with distinct tubercles : areolae quite close together : spines various ; outer white, 6-8, 

 radiant, 8-10 mm. long ; central solitary, 10-25 mm. long, yellowish brown : flowers pur- 

 ple, 5-10 cm. long : fruit ovoid, nearly 2 cm. long, green, furnished with bristles : seeds 1 

 mm. long, tuberculate. [Cereus Berlandieri Engelm.] 



In river valleys, southern Texas. 



5. Echinocereus procumbens ( Engelm. ) Small. Stems jointed, diffusely branched, 

 the joints nearly terete or 4-5-angled, 1.5-10 cm. long, 12-16 mm. thick, contracted at the 

 base, with 4 or 5 rows of distinct tubercles : spines rigid, rather slender ; outer white, 

 radiant, 5 or 4-6, 2-4 mm. long ; central solitary, stouter than the outer, 4-6 mm. long, 

 ascending or wanting : flowers delicate purple, fully 7.5 cm. long : fruit green, ovoid, 12-16 

 mm. long: seeds lenticular, nearly 1 mm. thick. [Cereus procumbens Engelm.] 



In river valleys, southern Texas. 



6. Echinocereus Pos61geri ( Coulter) Small. Stems weak, erect or reclining, sparingly 

 branched, the joints slender, 30-60 cm. long, 8-16 mm. thick, the ribs 8, not very promi- 

 nent, furnished with closely set areolae : spines bristle-like ; outer white, 9-12, straight, 

 barely 2 mm. long ; central solitary, 4-6 mm. long, whitish to brown or black : flowers rose 

 or purple, 5 cm. long and broad : fruit about 2 cm. long, clothed with white and black 

 bristles and wool : seeds less than 1 mm. long, tuberculate. [Cereus Poselgeri Coulter.] 



On rocky ridges, northern Texas and adjacent Mexico. 



3. CEREUS Mill. 



Plants with elongated cylindric prismatic or narrow angled or ribbed stems. Spine- 

 bearing areolae more or less remote. Leaves obsolete. Flowers arising from areolae 

 situated above fully developed spine-bearing areolae. Hypanthium prolonged beyond the 

 ovary. Styles slender. Stigmas several. Fruit fleshy or dry. Seeds smooth or pitted. 

 Embryo curved. 



