CEPHALOCEREUS. 25 



MONVILLBA sp. 



Stems slender, sometimes 3 to 4 meters high, nearly simple, rather weak and often supported 

 by other plants, 3 to 5 cm. in diameter; ribs about 8, 1 cm. high; areoles i to 1.5 cm. apart; radial 

 spines about 10, somewhat unequal, the longest about i cm. long; central spines 2 or 3, longer and 

 stouter than the radial, usually about 2 cm. long, black at tip; flowers and fruit not seen. 



Collected by J. N. Rose and George Rose near Guayaquil, Ecuador, August 11, 1918 

 (No. 22117). 



This species was quite common in the flat country northwest of Guayaquil associated 

 with a larger arborescent cactus, a species of Lcmaireocercus, and at first was supposed to 

 be its juvenile form. Unfortunately, no flowers or fruit were seen. Living specimens 

 were brought back to the New York Botanical Garden, but these have not yet flowered. 

 We are not certain of the generic position of this plant, but it so much resembles Mon- 

 villea maritima in habit that we suspect that its relationship is here. 



3. CEPHALOCEREUS Pfeiffer, Allg. Gartenz. 6: 142. 1838. 



Cephalophorus Leraaire, Cact. Aliq. Nov. xii. 1838. Not Cephalophora Cavanillc. 1S01. 

 Pilocereus Lemaire, Cact. Gen. Nov. Sp. 6. 1839. 



Elongated cacti, various in habit, mostly columnar and erect, sometimes much branched with 

 a short trunk or in one species with spreading and procumbent branches ; in some species the flower- 

 ing areoles develop an abundance of wool which confluently forms a dense mass called a pseudo- 

 cephalium either at the top or on one side near the top ; in others long wool or hairs grow from the 

 areoles but a pseudocephalium is not formed; in others the flowers are produced in a circle at the 

 top and the bristles and fruit afterwards form a collar at the base of the new growth ; in other species 

 neither wool nor hairs are produced in the flowering areoles; flowers nocturnal, short-campanulate to 

 short- funnelf orm or pyrif orm, straight or curved ; perianth persisting on the ripening fruit, except in 

 one species; fruit usually depressed-globose, sometimes oblong; seeds black, smooth or tuberculate. 



We know 48 species, distributed from southern Florida and northern Mexico to 

 eastern Brazil and Ecuador. The type species is Cactus senilis Haworth, which is also 

 the type of Lemaire's genera Cephalophorus and Pilocereus. The name Cephalocereus is 

 from the Greek, signifying headed-cereus, with reference to the pseudocephalium of the 

 typical species. 



Key to Species. 



A. Flowering areoles confluent, forming a pseudocephalium. 

 Pseudocephalium lateral. 



Ovary bearing few distant scales; areoles of the flower with tufts of short wool; 

 plants simple, tall, columnar. 

 Plant cylindric ; top rounded ; bristles of pseudocephalium twice as long as wool . 1. C. senilis 

 Plant tapering to the apex; bristles of pseudocephalium little longer than the wool. 2. C. hoppensledlii 

 Ovary naked. 



Plant unbranched 3. C. purpureus 



Plant branched at the base. 



Ribs 12 to 17; flowers 6 to 7 cm. long 4. C. fluminensis 



Ribs up to 23; flowers 4 cm. long 5. C. dybowskii 



Pseudocephalium terminal 6. C. macroccphalus 



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

 docephalium. 

 Flower-tube strongly bent about middle; areoles wholly without hairs; plant blue. . . 7. C. pentaedrophorus 

 Flower-tube straight or a little curved at the base. 

 Ribs 10 to 18; flowers red. 



Ribs 15 to 18; perianth-segments not reflexed 8. C. polylophus 



Ribs 8; perianth-segments reflexed 9. C. euphorbioides 



Ribs 4 to 13; flowers mostly whitish to purplish. 



Perianth falling away from the ovary by abscission 10. C. russelianns 



Perianth withering-persistent (so far as known). 

 Ribs strongly tubercled. 



Spines all brown, the radials widely spreading, the centrals stout, subulate. .11. C. gounellei 



Spines all yellow, aciculai, the radials only slightly spreading 12. C. zehntneri 



Ribs not tubercled. 



Flower-tube curved at base; areoles of the stem all densely long-woolly. ... 13. C. leucostele 

 Flower-tube straight; only flowering areoles, if any, long-woolly. 



