82 OPUNTIACEAE. 



2. HYLOCEREUS Britt. & Eose. Plants with climbing prominently 

 3-angled or 3-winged stems and branches, the areolae remote, with several short 

 spines and short wool. Hypanthium elongate, with succulent scales. Corolla 

 very large, white, the petals, like the sepals, long and narrow. Fruit scaly. 



1. H. tricostatus (Gosselin) Britt. & Eose. Stem and branches stout, often 

 8-12 cm. thick, bright-green, commonly high-climbing: areolae remote: spines 

 3-5, rigid, dark, usually 2-4 mm. long: corolla about 2 dm. wide: fruits ovoid, 

 8-10 cm. long, scarlet, the scales flat. NIGHTBLOOMING-CEREUS. 

 Hammocks, s. pen. Pla. and the F. Keys. Nat. of Mexico. (W. I.) 



3. CEPHALOCEREUS Pfeiff. Plants fleshy with ribbed usually branched 

 stems, the upper areolae usually developing wool. Leaves obsolete. Flowers 

 nocturnal, relatively small, one from an areolae. Hypanthium short, funnel- 

 form, with few scales. Sepals and petals fleshy. Ovary globular, spineless, 

 sometimes with few scales. Fruits fleshy, relatively small,- globular or depressed. 

 Seeds reticulate, shining. 



1. C. keyensis Britt. & Eose. Stem and branches erect or nearly so, becoming 

 5 or 6 m. tall, glaucous, the 9 or 10 ribs separated by deep grooves: areolae 

 1-2 cm. apart, slightly elevated : spines acicular, about 15, yellow, 15 mm. long, 

 or less: flowers brownish purple, about 6 cm. long, garlic-scented when opening 

 in the late afternoon or evening: sepals oblong-spatulate, blunt-tipped: petals 

 acutish: fruits spheroidal, about 3.5 cm. thick, reddish. 

 Hammocks, Key West. (Endemic.) 



4. HAKRISIA Britton. Plants fleshy with cylindric stems and fluted 

 branches, the shallow grooves with frequent areolae each of which supports 

 several slender spines. Leaves obsolete. Flowers nocturnal, relatively large, 

 borne near the ends of the branches. Hypanthium cylindric, spineless, scaly. 

 Sepals colored. Petals white. Fruits fleshy, globose to ovoid, spineless, but 

 scaly. Seeds small, often black. 



1. H. Brookii Britton. Stem and branches reclining or climbing, sometimes 5 

 m. tall, prominently 10-ribbed: areolae about 2 cm. apart: spines 9-12, the 

 longer ones 2-2.5 cm. long: fruits ellipsoid, rounded at both ends, about 8 cm. 

 long, yellowish, the tubercles with tips about 1.5 mm. high, becoming smooth. 

 Coastal hammocks, s. pen. Pla. and the F. Keys. (W. I.) 



5. OPUNTIA [Tourn.] Mill. Plants conspicuously jointed, with separated 

 usually spine-bearing areolae. Flowers arising from the areolae. Style cylin- 

 dric. Fruits fleshy or dry. PRICKLY-PEAR. 



Joints firmly attached to each other : flowers large : corolla 5 cm. wide or more. 

 Plants prostrate or diffusely branched. 



Plants prostrate : roots fibrous. 1. O. Opuntia. 



Plants diffuse : roots tuber-bearing. 2. O. austrina. 



Plants erect, bushy-branched. 



Spines copious : corolla yellow. 3. O. Dillenil. 



Spines none or imperfectly developed : corolla salmon or 



sometimes yellow. 4. O. inermis. 



Joints readily separating when shocked : flowers small : corolla 4 



cm. wide or less. 5. O. Pes-Corvi. 



1. O. Opuntia (L.) Coulter. Stems prostrate from fibrous roots, the joints 

 orbicular to obovate, pale or light green, 5-10 cm. long, bearing thick leaves 

 4-5 mm. long: bristle-cushions rather remote, usually unarmed: bristles few, 

 yellowish green: spines few, when present solitary, less than 2.5 cm. long, 

 variegated: flowers pale yellow, 5-6 cm. broad: fruits obovoid or clavate- 



