816 OPUNTIACEAE 



Leaves obsolete. Flowers nocturnal, relatively large. Hypanthiuni cylindric up to 

 the slightly expanded summit, with spiny areolae. Sepals green. Petals white. 

 Fruits fleshy, globose to oval, red or scarlet, spiny. 



1. Acanthocereus pent^gonus (L.) Britton & Eose. Similar to Hylocereus 

 triangularis in habit, but lacking the aerial roots. Stems sometimes S m. long, tl-je 

 joints various, a 3-angled one often arising from a 5-angled one: spines 5-8, the 

 radial bristle-like or subulate, brittle, the central one 1-2 cm. long: flowers white: 

 petals linear to linear-oblong, 2-3.5 cm. long, acute: fruits 5-S cm. long, opening 

 irregularly when mature. 



In sandy soil or cornl rock, southern peninsular Florida and the Keys. Also on the 

 coasts of the West Indies and in tropical America. 



7. CEPHALOCEREUS Pfeiff. 

 Plants fleshy with ribbed usually branched stems, the upper areolae usually 

 developing wool. Leaves obsolete. Flowers nocturnal, relatively small, one from an 

 areola. Hypanthium short, funnelform, 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. Cephalocereus Key^nsis Britton & Rose. 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. [Cereus monoclonos Chapm. 

 in part.] 



In hammocks, Key West, Florida. 



8. HARRISIA Britton. 



Plants fleshy with cylindric stems and fluted branches, the shallow grooves with 

 frequent areolae each of which support 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. Harrisia Brookli Britton. Stem and branches reclining or climbing, some- 

 times 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. [Cereus monoclonos Chapm. 

 in part.] 



In hammocks, coastal region of southern Florida and the Keys. Also in the Bahamas. 



9. OPUNTIA Mill. 



Plants conspicuously jointed, with separated usually spine-bearing areolae. 



Flowers arising from the cushions of remote bristles of the areolae. Style cylindric. 



Fruits fleshy or dry. 



Joints flat or nearly so. 

 Fruits fleshy. 



Joints firmly attached to each other: flowers large. 



Plants prostrate or diffusely branched: spines white or gray. 

 Corolla ,5-7 cm. wide: fruits 2.5-,3 cm. long. 

 Plants prostrate. 



Joints spineless, or with a solitary spine at each areola. 



Spines, when present, slender: seeds 4 mm. wide or less. 1. O. Opiinlia. 

 Spines stout: seeds 5 mm. wide or more. 2. O. PoUardi. 



Joints spiny, with 2-15 spines at each areola. 3. 0. humifusa. 



Plants diffuse: roots tuberous. 



Spines yellow: fruits 3.5-4.5 cm. long. 4. O. Roseana. 



Spines white or pink, or variegated: fruits 2.5-3.5 cm. long. 



Upper joints narrowly obovate: species campestrian. 5. O. macrorhiza. 

 Upper joints broadly oliovate: species Floridian. 6. O. austrina. 



Corolla 10-12.5 cm. wide: fruits about 6 cm. long. 7. O. grandijlora. 



Plants erect, bushy-branched 



Spines copious: corolla yellow. 

 Spines yellow. 



Spines stout, distinctly flattened. 8. 0. Dillenii. 



Spines slender, scarcely flattened. 



