42 MISSOURI BOTANICAL GARDEN. 
Parry, Amer. Nat. 9; 141.— Watson, Proc. Amer. Acad. 143 252. 
Bot. Calif. 2: 164.—Baker, Journ. Linn. Soc. Bot. 18: 221. — 
Gard. Chron. n. s. $3 492. n. s. 263 18. iii. 1: 772. f. 145.— 
Land of Sunshine. 10: 1. — Trelease, Rept. Mo. Bot. Gard. 43 193. 
pl. 6-9, 21.— Schimper, Pflanzengeographie. 669. f. 369. 
Y. arborescens Trelease, Rept. Mo. Bot. Gard. 8: 163. pl. 5, 49. 
(1892). — Coville, Contr. U. S. Natl. Herb. 4: 201. frontispiece. — 
Merriam, N. Amer. Fauna. 7: 353-8. frontispiece and pl. 13. — 
Sargent, Silva. 10:19. pl. 502. 
Large at length much branched rough-barked tree. Leaves spread- 
ing, less than .3 m. long, 15 mm. wide, plano-convex or triquetrous, 
striate, minutely denticulate, very rigid, pungently pointed. Inflorescence 
sessile, dense, often scabrous-hispid. Flowers sometimes puberulent, 
greenish-white, 25 to 50 mm. in diameter. Fruit ovoid, erect or var- 
iously directed, 50 to 100 mm. long; seeds 1012 mm. across, 1 to 1.5 
mm. thick. — Plates 6. 7. 85, f. 10. 87, f. 1. 
Mohave desert, California, to Detrital valley, Arizona, 
and the Beaverdam mountains, Utah. — Plate 84, f. 2. 
The Joshua tree of the Mohave desert region, the largest 
and most imposing of the Yucceae of the United States, 
which was first called Yucca Draconis (?) arborescens by 
Torrey, subsequently Y. brevifolia by Engelmann, and 
which is now commonly known as Y. arborescens, differs in 
its collective flower and fruit character about as much from 
typical Yuccas as does Hesperoyucca. In separating it from 
Yucca, I have thought best to apply to it as a generic name 
the sectional name Clistoyucca under which Dr. Engel- 
mann* separates it from the other species of Yucca, since 
there can be no question as to the applicability of that 
name to this particular tree, though Dr. Engelmann ¢ sub- 
sequently found it desirable to add Y. gloriosa to this sec- 
tion, to which the writer ¢ afterwards added Y. gigantea. 
Only the one species is known. 
YUCCA Linnaeus. 
Perianth open-campanulate, of nearly distinct thin lanceo- 
late or ovate-lanceolate segments. Filaments nearly free, 
* Bot. King. 496. Trans. Acad. Sci. St. Louis. $347. 
t Trans. Acad. Sci. St. Louis. 33213. 
t Rept. Mo. Bot. Gard. 93 142. 
