858 CONTRIBUTIONS FROM THE NATIONAL HERBARIUM. 



Flowering areoles at the base or on the side of the tubercles. 

 Ovary more or less scaly (not known in Mamillopsis). 

 Flowers with a short tube. 



Spines partly hooked 39. ANCISTROCACTUS. 



Spines not hooked. 

 Tubercles not deeply grooved ; fruit scaly. 



40. THELOCACTUS. 

 Tubercles deeply grooved ; fruit nearly naked. 



41. NEOLLOYDIA. 



Flowers with an elongate tube 42. MAMILLOPSIS. 



Ovary naked or nearly so. 



Flowers irregular 43. COCHEMIEA. 



Flowers regular. 



Flowers central, borne in axils of young, usually nascent 

 tubercles. 

 Tubercles grooved on upper side. 



Seeds mostly light brown ; fruit greenish or yellowish, 



ripening slowly 44. CORYPHANTHA, 



Seeds black or dark brown ; fruit red, maturing rapidly. 



45. ESCOBARIA. 

 Tubercles not grooved on upper side. 



Fruit circumscissile ; tubercles fleshy ; spines acicular. 



46. BARTSCHELLA. 

 Fruit not circumscissile ; tubercles woody ; spines 



pectinate 47. PELECYPHORA^ 



Flowers lateral, borne in axils of old and mature tubercles, 

 these never grooved above. 

 Flowers large, with an elongate tube; tubercles elongate, 



flabby 48. DOLICOTHELK 



Flowers small, campanulate ; tubercles not flabby. 



Hilum of seed large; spines pectinate 49. SOLISIA. 



Hilum of seed minute; spines not pectinate. 



50. NEOMAMMILLARIA. 



1. PERESKIA Mill. Gard. Diet. Abr. ed. 4. 1754. 



Leafy trees or shrubs, or sometimes clambering vines, branching and re- 

 sembling other woody plants ; spines in pairs or in clusters in the axils 

 of the leaves, neither sheathed nor barbed ; leaves alternate, broad, flat, 

 deciduous, somewhat fleshy ; flowers solitary, corymbose, or in panicles, ter- 

 minal or axillary, wheel-shaped ; stamens numerous ; style one ; stigma lobes 

 linear; seeds black, glossy, with a brittle shell, the embryo strongly curved, 

 the cotyledons leafy ; seedlings without spines. 



Pereskia portulacifolia (L.) Haw. has often been reported incorrectly from 

 Mexico. The following vernacular names have been given for it : " Pitahayita 

 de agua " (Jalisco) ; " pata de leon," " patilon " (Oaxaca). The name " palo 

 de puerco espino " is reported from Oaxaca for a Pereskia whose specific 

 identity is doubtful. 

 Plants climbing vines ; branches with a pair of reflexed spines at each 



areole 1. P. aculeata. 



Plants erect shrubs or trees ; branches with straight spines at the areoles. 



Petals fimbriate 2. P. lychnidiflora. 



Petals entire. 



