26 



THE CACTACEAE. 



Key to Species — continued. 



AA. Flowering areoles not confluent, though sometimes close together, not forming a pseu- 



docephalium — continued. 

 Ovary well-developed; flower-tube little scaly or without scales. 

 Flowering areoles without wool, or wool very short. 



Fruit oblong to ovoid H; C. smithianus 



Fruit globose or depressed. 

 Spines acicular; berry large. 



Perianth-segments rounded, acute, or mucronate. 



Plant grayish green; at least the perianth-segments rounded 

 or mucronate. 



Outer perianth-segments rounded 15. C. bahamensis 



All perianth-segments rounded 16. C. deeringii 



Plant glaucous green when young, dull green when old; outer 

 perianth-segments acute. 

 Much branched, the branches ascending ; ribs 10 to 13; style 



exserted 17- C. robinii 



Little branched, the branches nearly erect ; ribs 9 or 1 o ; style 



scarcely exserted ; young growth very glaucous. 18. C. keyensis 



Perianth-segments retuse iQ- C. monoclonos 



Spines subulate; berry small 20. C. scoparius 



Flowering areoles definitely long-woolly. 

 Ribs 5 to 13, separated by narrow valleys. 

 Ribs 8 mm. high oi higher. 



Plant light green to dark green. 



Spines short, subulate 21. C. moritzianns 



Spines slender, acicular. 



Wool of flowering areoles sparse, not matted 22. C. arrabidae 



Wool of flowering areoles mostly copious, matted. 



Wool of flowering areoles brown 23. C. urbaniamts 



Woo! of flowering areoles white. 

 Plant bright green, shining. 



Joints slender, dark green; wool short 24. C. nobilis 



Joints stout, light green; wool long 25. C. barbadensis 



Plant dull green, not shining. 



Wool elongated, up to 5 to 7 cm. long 26. C. millspaughii 



Wool short, 2 cm. long or less. 

 Ribs 1 to 2 cm. high. 



Only the flowering areoles woolly 27. C. swarlzii 



Both flowering and flowerless areoles of young 



joints woolly 28. C. polygonus 



Ribs 8 mm. high or less 29. C. gaumeri 



Plant, at least young joints, blue or bluish green, glaucous. 

 Young spines yellow. 



Flower 7 to 8 cm. long 3°- C. chrysacanthus 



Flower 5 to 6 cm. long. 



Ribs 6 to 8 31- C. maxonii 



Ribs mostly 9 to 12. 



Ribs 13 32. C. piauhyensis 



Ribs 9 or 10. 



Perianth-segments rounded or mucronate. 



Young joints bright blue; ribs low 33. C. lanuginosus 



Young joints bluish green, glaucous; ribs high. . .34. C. brooksianus 



Perianth-segments acute 35. C. royenii 



Young spines brown or nearly black. 



Areoles approximate, their spines overlapping 36. C. robusius 



Areoles separated, their spines not overlapping. 

 Ribs 9 to 12. 



Wool short, 2 cm. long 37- C. comeles 



Wool 10 cm. long. 38. C. leiicocephalus 



Ribs 7 to 9. 



Ribs strongly horizontally grooved below the areoles. 



Flowers rose-red 39- C. sartorianus 



Flowers brown 4°- C. palmeri 



Ribs not grooved 41. C. tweedyanus 



Color of plant and of young spines unknown. 



Mexican 4 2 - C. alensis 



Colombian. . 43- C. colombianus 



Ribs only 5 to 6 mm. high; plant green 44. C. purpusii 



Ribs 4 to 6, separated by broad valleys. 



Glaucous, up to 10 meters high; flowers 6 to 8 cm. long 45. C. catingicola 



Bright green, up to 3 meters high; flowers about 5 cm. long 46. C. brasiliensis 



Ovary very short and flat; flower-tube scaly 47- C. phaeacanlhus 



AAA. Species not grouped •• 4 s - C. ulei 



