i6 



THE CACTACEAE!. 



white, with black tips; central spines i to 3, brown, stouter than the radials; flowers nocturnal, 10 

 to 12 cm. long; inner perianth-segments white, lanceolate, acuminate, 10 cm. long, the margins 

 dentate; stamens numerous, green; style longer than the stamens, green; stigma-lobes 14, spreading, 

 linear ; ovary glabrous, bearing a few scales ; fruit not known. 



Type locality: Brazil. 



Distribution: Brazil. 



The illustration of Schumann, here cited, resembles the species of Argentina more than 

 those of Brazil. Cereus azureus is reported growing in the Hanbury Garden at La Mortola, 

 Italy, and plants are now to be seen in the New York Botanical Garden, where one flowered 

 in 1915. 



Illustration: Schumann, Gesamtb. Kakteen f. 26. 



Fig. 15. — Cereus obtusus. 



Fig. 16. — Cereus aethiops. 



20. Cereus chalybaeus Otto in Forster, Handb. Cact. 382. 1846. 



Piptanthocereus chalybaeus Riccobono, Boll. R. Ort. Bot. Palermo 8: 227. 1909. 



Stems 2 to 3 meters high, with few ascending branches; ribs 6, very high on the young parts 

 of the stems and there separated by wide intervals, more or less purplish; radial spines usually 7, 

 but on old stems much more numerous; central spines several, a little longer than the radials, all 

 dark brown; perianth large, about 2 dm. long and about as broad when fully expanded; flower-tube 

 about 1 dm. long, purplish, bearing long tubercles crowned by minute scales; outer perianth- 

 segments pinkish, narrowly oblong, the inner white, acute, sometimes toothed ; filaments numerous, 

 long-exserted beyond the throat, but shorter than the perianth-segments; style elongated, much 

 longer than the filaments, weak; stigma-lobes many; fruit spherical, smooth, yellow. 



Type locality: Not cited. 

 Distribution: Northern Argentina. 



