STANDLEY TREES AND SHBUBS OF MEXICO. 913 



Widely cultivated in Mexico and often naturalized. Native country not 

 known, but widely distributed in cultivation in the tropics; originally de- 

 scribed from Chinese plants. 



Stem long, clambering over bushes and trees or creeping up the sides of 

 walls; ribs mostly 3, broad, thin, green; margin usually strongly undulate, 

 more or less horny in age ; areoles 3 to 4 cm. apart ; spines 1 to 3, small, 2 

 to 4 mm. long ; flowers up to 29 cm. long or more ; outer perianth segments 

 yellowish green, all turned back, some strongly reflexed ; inner perianth seg- 

 ments pure white, erect, broad, oblanceolate, entire, with apiculate tips; fruit 

 oblong, 10 to 12 cm. in diameter, red, covered with large foliaceous scales, or 

 nearly smooth when mature; seeds black. " Pitahaya " (Jalisco, Yucatan, 

 Costa Rica, El Salvador, Porto Rico); "pitahaya orejona " (Oaxaca, Reko) ; 

 "tasajo" (Durango, Patoni) ; " junco," " juco tapatio " (Consatti) ; " cha- 

 coub," " zacoub " (Yucatan); " caliz " (Philippines). 



This species has often been reported from Mexico as Cereus triangularis 

 (a species known only from Jamaica) and as C. trigonns. The large fruit is of 

 excellent quality and is much eaten. Grosourdy reports that the juice of the 

 stems is acrid and caustic and is employed externally and internally as a 

 vermicide, although internal use is dangerous. The plant is the best known 

 of all the night-blooming cereuses, and produces very showy flowers. 



22. SELENICEREUS Britt. & Rose, Contr. U. S. Nat. Herb. 12: 429. 1909. 



Slender, trailing, climbing or clambering, elongate cacti, (he joints ribbed or 

 angled, irregularly giving off aerial roots; areoles small, sometimes elevated 

 on small knobs, bearing small spines or in one species spineless; flowers large, 

 often very large, nocturnal; flower tube elongate, somewhat curved; scales of 

 ovary and flower tube small, usually with long felt, hairs, and bris- 

 tles in their axils; upper scales and outer perianth segments similar, nar- 

 row, greenish, brownish, or orange; inner perianth segments broad, white, 

 usually entire; filaments elongate, weak, numerous, in two clusters distinctly 

 separated, one cluster forming a circle at top of flower tube, the other scattered 

 over the long slender throat ; style elongate, thick, often hollow ; stigma lobes 

 slender, numerous, entire; fruit large, reddish, covered with clusters of decid- 

 uous spines, bristles, and hairs. 



Several other species occur in tropical America. 



Areoles of flower tube and ovary without long hairs. 



Spines of the branch areoles acicular 7. S. vagans. 



Spines of the branch areoles short, conic. 



Ribs 7 or 8, obtuse ; spines from areoles on ovary 1 to 3 8. S. murrillii. 



Ribs 4 to 6, acute; spines from areoles on ovary 10 or more. 



9. S. spinulosus. 

 Areoles of flower tube and ovary bearing long hairs. 



Branches with a stout deflexed spur under each areole 6. S. hamatus. 



Branches not spurred. 



Spines of branch areoles acicular. 



Hairs of flower areoles tawny or whitish 1. S. grandiflorus. 



Hairs of flower areoles bright white 2. S. coniflorus. 



Spines of branch areoles short, conic. 

 Branches 9 or 10-ribbed ; branch areoles with many appressed linirs. 



3. S. donkelaarii. 

 Branches 4 to 6-ribbed ; young branch areoles with few long hairs. 



Stems stout, 3 to 5 cm. thick 4. S. pteranthus. 



Stems slender, 1.5 to 3 cm. thick 5. S. boeckmannii. 



