STANDLEY TREES AND SHRUBS OF MEXICO. 871 



2. Opuntia leptocaulis DC. Mem. Mus. Hist. Nat. 17: 118. 1828. 



Opuntia ramnlifera Salm-Dyck, Hort. Dyck. 360. 1834. 



Opuntia gracilis Pfeiff. Enum. Cact. 172. 1837. 



Opuntia virgata Link & Otto; Forst. Handb. Cact. 506. 1846. 



Opuntia vaginata Engelm. in Wisliz. Mem. North. Mex. 100. 1848. 



Opuntia frutescens Engelm. Best. Journ. Nat. Hist. 6: 208. 1850. 



Widely distributed in Mexico, extending southward to Puebla. Also in the 

 southwestern United States. 



Usually bushy, often compact, 2 meters high or less, but sometimes with a 

 short definite trunk 5 to 8 cm. in diameter, dull green with darker blotches 

 below the areoles, with slender, cylindric, ascending, hardly tuberculate 

 l)ranches ; branches, especially the fruiting ones, thickly set with short, usu- 

 ally spineless joints spreading nearly at right angles to the main branches, 

 very easily detached ; spines usually solitary at young areoles, very slender, 

 white, at areoles of old branches 2 or 3 together, 2 to 5 cm. long or less : are- 

 oles with very short white wool ; flowers greenish or yellowish, 1.5 to 2 cm. 

 long (including the ovary) ; ovary obconic, bearing numerous small woolly 

 brown areoles subtended by small leaves, its glochids brown ; fruit globular 

 to obovate or even clavate, often proliferous, red or rarely yellow, 10 to 18 

 mm. long, slightly fleshy. " Tasajillo " (Durango, Nuevo Leon, Tamaulipas, 

 Chihuahua, Texas, New Mexico). 



The plant is abundant in many parts of northern Mexico and often forms 

 dense thickets. The long spines are very offensive, and often cause bad sores 

 wlien they penetrate the flesh. 



Opuntia ramosissima Engelm.,* a closely related species, common in south- 

 western Arizona, should be looked for in Sonora and Baja California. 



Opuntia tesajo Engelm." was based on a Baja California specimen, but the 

 type has been lost, and the plant should perhaps be referred to 0. leptocaulis. 



3. Opuntia arbuscula Engelm. Proc. Amer. Acad. 3: 309. 1856. 



Sonora. Southwestern United States; type from the lower Gila, near Mari- 

 copa Village. 



Forming a bush 2 to 3 meters high, often with a rounded, very compact top 

 with numerous short branches; trunk short, 10 to 12 cm. in diameter, with 

 several woody branches; ultimate joints 5 to 7.5 cm. long. 8 mm. in diameter, 

 with low indistinct tubercles; spines usually 1, but sometimes several, espe- 

 <;ially on old joints, porrect, up to 4 cm. long, covered with loose straw-colored 

 sheaths ; flowers greenish yellow tinged with red, 3.5 cm. long ; fruit often 

 proliferous, sometimes only one-seeded. 



4. Opuntia kleiniae DC. Mem. Mus. Hist. Nat. 17: 118. 1828. 

 Opuntia tvrightii Engelm. Proc. Amer. Acad. 3: 308. 1856. 

 •Opuntia caerulescens Griffiths, Rep. Mo. Bot. Gard. 20: 86. 1909. 

 Central and northern Mexico. Southwestern United States. 



Stems pale, glaucous, sometimes 2.5 meters tall, woody at base; tubercles 

 long; areoles large, a little longer than wide, filled with white wool from the 

 very first; spines usually 1, but sometimes more, from the base of the areole, 

 covered with yellow sheaths, on old joints accompanied by several bristle-like 

 spines from the lower margin of the areole ; glochids yellow to brown ; flowers 

 3 cm. long, purplish ; petals broad, rounded at apex ; fruit red. 2 to 2.5 long, 

 long persisting; seeds 4 to 5 mm. broad. "Tasajillo" (Durango, Patoni). 



'Amer. Journ. Sci. II. 14: 339. 1852. 

 'Coulter, Contr. U. S. Nat. Herb. 3: 448. 1896. 



