Vol. XXIX, pp. 9-16 January 25, 1916 



PROCEEDINGS 



OF THE 



BIOLOGICAL SOCIETY OF WASHINGTON 



NEW SPECIES OF OPUNTIA. 

 BY DAVID GRIFFITHS. 



This seventh * installment of formal descriptions of new 

 species of Opuntia has been somewhat delayed to secure more 

 complete data from the mature cultivated plants. The types 

 will be preserved in the U. S. Department of Agriculture and 

 duplicates will be prepared for other herbaria. 



Opuntia magnarenensis sp. nov. 



A large hemispherical shrub 100-125 cm. high and 2 m. in diameter 

 when fully developed, with main arms radiating and either ascending or 

 resting on their edges, the secondary ones always erect from them ; joints 

 obovate, sometimes widest at middle, but usually widest slightly above 

 middle, pointed both above and below, yellowish-green, slightly glaucous, 

 about 18 by 30 cm. ; leaves very large, flattened, prominently acuminate- 

 cuspidate, 10-12 mm. long; areoles very large, oval to obovate, the largest 

 ones on edges of last year's joints commonly 4 by 6 mm. and smallest 

 about 3 by 5 mm., brown turning prominently gray and enlarging with 

 age; spicules yellow, very prominent, scattered, unequal, 1 to 1)4 cm. 

 long, increasing tremendously with age in both length and numbers, the 

 areoles becoming very prominent ; spines white with light, bright reddish 

 bases, flattened, stout, not annular, spreading in all directions, some- 

 times twisted, 2-5 mostly 3, the central upper one very long and porrect, 

 3-5 cm. long, others shorter spreading around it; flowers yellow, 7 cm. 

 in diameter, filaments yellow, style white to greenish tinged, stigma dark 

 green, 7-parted, buds dull greenish-red, pointed, with lax sepals; fruit 

 purplish-red throughout, with abundant bloom, long, obovate, about 4 

 by 7 cm., its areoles tawney, about 20, bearing spicules 4 mm. long. 



This species is common on the Big Sandy, 30-50 miles south of King- 

 man, Arizona. It is one of the conspicuous species on the bench lands 

 above the river bottoms. In its main characteristics, it resembles more 



• Ptoc. Biol. Soc. Wash. 27 : 23. 1914. 



3— Proc. Biol. Soc. Wash.. Vol. XXIX. 1916. (9) 



