42 MISSOURI BOTANICAL GARDEN. 



Parry, Amer. Nat. 9: 141. Watson, Proc. Amer. Acad. 14: 252. 

 Bot. Calif. 2: 164. Baker, Journ. Linn. Soc. Bot. 18: 221. 

 Gard. Chron. n. s. 3 : 492. n. s. 26: 18. iii. 1: 772. /. 145. 

 Land of Sunshine. 10: 1. Trelease, Kept. Mo. Bot. Gard. 4 : 193. 

 pi. 6-9, 21. Schiraper, Pflanzengeographie. 669. /. 369. 

 Y. arborescens Trelease, Kept. Mo. Bot. Gard. 3: 163. pi. 5, 49. 

 (1892). Coville, Contr. U. S. Natl. Herb. 4: 201. frontispiece. 

 Merriam, N. Amer. Fauna. 7: 353-8. frontispiece and pi. 13. 

 Sargent, Silva. 10: 19- pi- 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 100mm. long; seeds 10X12 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. brevi folia 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 f sub- 

 sequently found it desirable to add Y. gloriosa to this sec- 

 tion, to which the writer J 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. 3 : 47. 

 t Trans. Acad. Sci. St. Louis. 3:213. 

 J Kept. Mo. Bot. Gard. 9 : 142. 



