194 



THE CACTACEAE. 



horses. The wide distribution of the species is doubtless largely due to the fact that the 

 joints are so easily scattered. A hybrid with 0. tortispina has been found in Kansas 

 (Rose, No. 1 7132). 



The plant is of especial interest as the most northern in distribution of the opuntias. 



It is stated that Opuntia cervicomis Spath (Cat. 156. 1906-7) is "probably a hybrid 

 of which 0. fmgilis is a parent" (Kew Bull. Misc. Inf. 1907: App. 74. 1907). 0. sabinii 

 (Pfeiffer, Enum. Cact. 147. 1837) was given as a synonym of 0. fragilis. 



Illustrations: Cact. Journ. i: 100; Diet. Card. Nicholson 2: f. 752; Forster, Handb. 

 Cact. ed. 2. f. 132; Gartenfiora 30: 413; Pac. R. Rep. 4: pi. 12, f. 9; Riimpler, Sukkulenten 

 f. 126; W. Watson, Cact. Cult. f. 78; Wiener lUustr. Gartenz. 10: f. 113, all as Opuntia 

 brachyarthra. lUustr. Fl. 2 : f. 2532 ; ed. 2. 2 : f . 2991 ; Pac. R. Rep. 4 : pi. 24, f. 5. 



Plate XXXV, figure i, shows old and young joints of the plant collected by C. Birdseye 

 at Florence, Montana, in 1910. Figure 239 is from a photograph of the plant taken by 

 B- R. Warren at San Acacio, Colorado, in 1912. 



— < ipiiiitia fragilis. 



217. Opuntia arenaria Engelmann, Proc. Amer. Acad. 3: 301. 1S56. 



Roots in clusters of 10 to 15, spindle-form, somewhat fleshy; stem prostrate, 2 to 3 dm. long, 

 much branched; joints during growing season quite turgid, afterwards much thinner, 4 to 8 cm. 

 long, half as broad as long; areoles large, numerous, filled with brown wool, glochids, and spines; 

 spines 5 to S from an areole, 2 or 3 much longer than the others, sometimes 4 cm. long; flowers red, 

 7 cm. broad; fruit Axj, spiny, 3 cm. long; seeds large, 7 cm. broad. 



Type locality: Sandy bottoms of the Rio Grande near El Paso. 



Distrihiition: Texas and southern New Mexico. 



This species is very rare and has been reported only a few times. Dr. Rose, who has 

 repeatedly collected at El Paso, was never able to find it until October 19 13, and then but 

 a single plant about 8 miles above El Paso on the New Mexican side of the Rio Grande. It 

 grows in nearly pure sand not far above the level of the river. 



