30 THE CACTACEAE. 



Type locality: Guadalajara, Mexico. 



Distribution: In hedges about Guadalajara, Mexico. 



The fruit, called in Mexico tuna de agua and tasajillo, is used in making a cooling 

 drink and for preserves. 



Opuntia spathnlata aquosa (Bull. Mus. Hist. Nat. Paris 4: 165. 1898) was given as a 

 synonym of this species, but was never published. 



Illustration: Safford, Ann. Rep. Smiths. Inst. 1908: pi. 10, f. 2. 



Figure 27 represents a leafy shoot of the plant collected by W. E. Safford near 

 Guadalajara, Mexico, in 1907. 



10. Pereskiopsis kellermanii Rose, Smiths. Misc. Coll. 50: 332. 1907. 



Stem glabrous, herbaceous, weak, and clambering over shrubs to a length of 4 to 5 meters, 

 about 2 cm. in diameter; second-year branches usually at right angles to main stem, with cherry- 

 red bark; old stem bearing several slender, acicular brown spines, sometimes only i, sometimes 

 wanting, and numerous brown glochids; young branches green, fleshy, their areoles circular, white, 

 filled with long white hairs, brown glochids, and often with several 

 acicular brown spines; spines on wild plants often stout, usually 

 solitary, nearly black, 2 to 3 cm. long; leaves various, shining green, 

 glabrous, thickish, elliptic and two or three times as long as wide, 

 or suborbicular, acute at the apex, narrowed at the base, 5 cm. long 

 or less, 2 to 2.5 cm. broad; flowers not known; fruit red, glabrous, 

 leafy, 3 to 6 cm. long, bearing large areoles filled with brown 

 glochids; seeds covered with matted hairs. 



FIGS 28, 29, and 30. Pereskiopsis keller- 

 TypC locality. Trapicllite, Guatemala. manii, showing three leaf forms. Xo.5. 



Distribution : Guatemala. 



Figures 28, 29, and 30 are copied from sketches of the leaf-forms of the type plant, 

 made by W. A. Kellerman in Guatemala in 1908. 



2. PTEROCACTUS Schumann, Monatsschr. Kakteenk. 7: 6. 1897. 



Stems low, more or less branched above, cylindric, from tuber-like and often greatly enlarged 

 roots; leaves minute, caducous; spines weak, several or many at each areole; glochids small, cadu- 

 cous as in Opuntia; flower terminal, regular, without tube; perianth-segments several, erect; fila- 

 ments and pistil shorter than the petals; ovary nearly turgid, bearing numerous small clusters of 

 spines; fruit dry, capsular, dehiscent; seeds winged, white; embryo curved. 



Type species: Ptcrocactus kuntzei Schumann. 



Four species have already been described, but three of these we have combined and 

 the fourth is referred to Opuntia. Three additional species, however, are here described. 

 The generic name refers to the winged seeds. 



This is a remarkable genus, and it is surprising that it remained unrecognized so long, 

 for one of its species was known as long ago as 1837 ; the fruit and seeds, however, seem not 

 to have been known until about 1897. In habit the plants are nearest some of the anom- 

 alous species of Opuntia, having large roots and short, weak stems like Opuntia chaffeyi, 

 of Mexico; the seeds, however, differ, not only from those of Opuntia, but from those of 

 all other cactus genera, in being winged. The fruit, according to Schumann, although 

 we have not been able to confirm his observation definitely, is a capsule with an opercu- 

 lum. Another peculiarity is that the fruit is borne in the end of the stem or branch. 



While this genus has good characters, it is no more distinct than many others and does 

 not deserve the relative importance given to it by T. von Post and Otto Kuntze in Lexicon 

 Generum Phanerogamarum, who treat it as one of the only three cactus genera to be 

 conserved, in their view. 



