15° 



Joshua Tree 



I. JOSHUA TREE 



GENUS CLISTOYUCCA [ENGELMANN] TRELEASE 



Species Clistoyucca arborescens (Torrey) Trelease 



Yucca Draconis arborescens Torrey 



Yucca hrevijolia Engelmann, not Schott. Yucca arborescens Trelease 



HIS interesting tree occurs in the Mojave desert region of southern 



California, eastward into Arizona and southwestern Utah, attaining a 



height of 12 meters, with a trunk diameter of 9 dm., and is also known 



as Joshu yucca, Tree yucca, Yucca cactus, and The joshua. 



The tnmk is thickened near the ground, contracted just above, and with the 



exception of very old trees is densely clothed 

 to the base by the persistent dead leaves. 

 The rind at the base of the trunk is 2.5 to 4 

 cm. thick, deeply fissured into narrow thick 

 elongated plates of a grayish color. The 

 branches usually appear after the plant has 

 first flowered, and fork repeatedly after 

 further flowering, forming a broad open head. 

 The leaves are densely clustered at the ends 

 of the branches, b'ght green, somewhat glau- 

 cous, 1.25 to 3 dm. long, 6 to 12 mm. wide, 

 abniptly narrowed just above the shining 

 red-brown base, concave above, flattened 

 toward the base, the tip dark reddish brown, 

 stiff, tapering and sharp, the margin thin, 

 yellowish, finely toothed. The flowers ap- 

 pear in spring from a large hairy ovoid 

 bud, in hairy densely flowered sessile panicles 

 about 4 dm. long; the upper bracts are 

 white and dryish; the flowers are erect, 

 globose or oblong, 2.5 to 5 cm. long, greenish 

 white and unpleasantly odorous; the perianth-segments are keeled on the back, 

 thickened above the middle, the tip inflexed and much thickened ; those of the outer 

 series are broader and thicker than those of the iimer, oblanceolate to lanceolate ; 

 stamens about one half the length of the perianth, their filaments nearly free, 

 thickened, and usually curved outwardly above ; anthers arrow-shaped ; ovary sessile, 

 ovoid, tapering upward into the 6-lobed stigma. The fruit is somewhat drooping 

 when ripe, oblong or ovoid-oblong, 5 to 10 cm. long, somewhat 3-lobcd, and 

 sharp-pointed ; it is light brown or yellow-brown, indehiscent, dry, its spongy wall 

 about I cm. thick, enclosing the many black seeds; these are roundish-triangular, 

 10 to 12 mm. long, 1.5 mm. thick, with a narrow margin. 



Fig. III. — Joshua Tree. 



