OPUNTIA. 47 



KEY TO SPECIES. 



Ultimate joints short, usually at right angles to the branches, 4 to 7 mm. thick. 

 Bushy plants, 1.5 meters high or less; fruit small, fertile. 

 Branches scarcely if at all tuberculate. 



Leaves ovoid to ovoid-subulate; young arcoles long-hairy 2. 0. mortolensis 



Leaves linear; areoles not long-hairy 3. O. leplocaulis 



Branches long-tuberculate 4. 0. tesajo 



Elongated plants, up to 2 meters long; fruit larger, sterile 5. O. caribaea 



Ultimate joints longer, 8 to 15 mm. thick, usually at an acute angle to the branches. 



Joints only slightly tuberculate 6. 0. arbuscula 



Joints manifestly tuberculate 7. 0. kleiniae 



2. Opuntia mortolensis sp. nov. 



Slender, 6 dm. high or less, dull green, with dark blotches below the areoles, the ultimate twigs 

 short, sometimes only 2 cm. long, 4 to 5 mm. thick, scarcely tuberculate; leaves ovate to ovate- 

 subulate, 2 to 4 mm. long, green, with acute bronze-colored tips; young areoles with numerous, early 

 deciduous, weak white hairs sometimes longer than the leaves, and several brown glochids; areoles 

 of old branches with solitary acicular spines 3 to 5 cm. long, these with tightly fitting brownish sheaths ; 

 flowers and fruit unknown. 



Described from No. 25360, New York Botanical Garden, received from the garden of 

 Sir Thomas Hanbury, La Mortola, Italy, in 1906. Mr. Berger has referred this specimen 

 to Opuntia leptocaulis longispina, but this was considered by Dr. Engelmann as the "usual 

 western form" of 0. leptocaulis. 



An herbarium specimen collected by Rose, Standley, and Russell at Empalme, Sonora, 

 Mexico, March n, 1910 (No. 12644), appears to be referable to this species. 



The short leaves and long-hairy young areoles appear to distinguish this plant from 

 0. leptocauUs. 



Illustration: Card. Chron. III. 34: f. 37, as Opuntia leptocauUs longispina. 



Plate vi, figure i, represents a branch of a plant sent from La Mortola, Italy, in 1906; 

 figure 2 shows a leafy twig of the same plant. 



3. Opuntia leptocaulis De Candolle, Mem. Mus. Hist.'Nat. Paris 17: 118. 1828. 



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



Opuntia gracilis Pfeiffer, Enum. Cact. 172. 1837. 



Opuntia fragilis frute see ns Engelmann, Bost. Journ. Nat. Hist. 5: 245. 1845. 



Opuntia virgata Link and Otto in Forster, Handb. Cact. 506. 1846. 



Opuntia vaginata Engelmann in Wislizenus, Mem. Tour North. Mex. 100. 1848. 



Opuntia frutescens Engelmann, Bost. Journ. Nat. Hist. 6: 208. 1850. 



Opuntia frutescens brevispina Engelmann, Proc. Amer. Acad. 3: 309. 1856. 



Opuntia frutescens longispina Engelmann, Proc. Amer. Acad. 3: 309. 1856. 



Opuntia leptocaulis brevispina S. Watson. Bibl. Index 1 : 407. 1878. 



Opuntia leptocaulis vaginata S. Watson, Bibl. Index 1 : 407. 1878. 



Opuntia leptocaulis stipata Coulter, Contr. U. S. Nat. Herb. 3: 456. 1896. 



Opuntia leptocaulis longispina Berger, Bot. Jahrb. Engler 36: 450. 1905. 



Usually bushy, often compact, 2 to 20 dm. high, 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 branches; branches, especially the fruiting ones, thickly set with short, usually 

 spineless joints spreading nearly at right angles to the main branches, very easily detached ; leaves 

 green, awl-shaped, 12 mm. long or less, acute; 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 ; sheaths of spines closely fit- 

 ting or loose and papery, yellowish brown to whitish; areoles with very short white wool; flowers 

 greenish or yellowish, 1.5 to 2 cm. long including the ovary; sepals broadly ovate, acute, or cuspidate; 

 ovary obconic, bearing numerous small woolly brown areoles subtended by small leaves, its glochids 

 brown; fruit small, globular to obovate or even clavate, often proliferous, red or rarely yellow, 10 

 to 1 8 mm. long, turgid, slightly fleshy; seeds compressed, 3 to 4 mm. broad, with narrow, often 

 acute, margins. 



Type locality: In Mexico. 



Distribution: Southwestern United States and Mexico. 



This species has a wide distribution for an Opuntia, extending from southern United 

 States to Puebla, Mexico. 



