FOREST TREES OF THE PACIFIC SLOPE. 203 



Trunks 10 feet high may he entirely covered. Gradually these dead, but always 

 stiff and prickly, leaves are forced off at the base of the trunk by the growth of 

 the trunk and by wind, uncovering an ashy, gray, cross-checked and ridged 

 bark. Except on old trees, the greater part of the tree is covered with dead, 

 closely thatched leaves. This covering of formidable living and dead leaves 

 suggests a wise protective measure through which alone the tree is able to 

 maintain and extend itself, with little check from its enemies, in a region often 

 lacking in other vegetation. The bluish-green leaves (fig. 80, a) are from to 

 about 10 inches long and about five-eighths of an inch wide ; longer leaves occur 

 on young trees. Leaves taper gradually from just above the base (1J inches 

 wide) to the point. The upper half is concave, tapering to a long, keen, red- 

 dish or blackish brown point: the lower half of the leaf is flat or only slightly 

 concave, while the two edges have minute teeth throughout. A single stiff, 

 branched cluster (about 15 inches long) of rather fetid flowers grows from the 

 end of the crown branches. The fruit (fig. 79, b), usually matured early in Juno, 

 is borne on short stems, at first standing more or less erect, but after maturity 

 somewhat drooping or bent down. The fruit covering is dry and soft. It rarely 

 opens of its own accord, but when very dry and brittle it is blown or falls from 

 the tree, and later is blown about and broken open by the wind and its seed 

 scattered. The six chambers of the fruit are filled with flat, jet-black seeds 

 I fig. 79, c, d). Wood rather soft and light (when dry), but tough on account 

 of its strong fibers; pale yellowish white. Further investigation may estab- 

 lish its permanent usefulness for paper pulp, for which it is suitable." 



Longevity. — Nothing can be said definitely of the age to which this tree 

 attains. It is very probable that an individual lives at least 100 to 200 years, 

 and there seems little doubt that these trees may live 200 to 300 years. The 

 growth appears to be very slow in both height and diameter, but very persistent. 

 Its big, strong roots descend to great depths, giving the tree*; firm anchorage. It 

 is frequently bent and bowed, but few trees succumb to storm, and not often to 

 fire, which does not burn their stiff, hard leaves as readily as in the case of the 

 thinner and more inflammable leaves or "thatch" palm trunks. 



RANGE. 



Southwestern Utah to the western and northern rim of the Mohave Desert in 

 California. 



OCCURRENCE. 



Arid, desert plains and valleys, lower mountain slopes, benches, and plateaus, in dry, 

 sandy and gravelly soils. Forms large pure, open or rather close stands ; sometimes 

 much scattered singly and in groups and with California juniper and single-leaf and 

 Sabine pines. Low, scanty growths of cactus and other desert shrubs occur with the 

 yucca. 



Climatic Conditions. — Similar to those of California juniper (with probably higher 

 temperature). 



Tolerance and Reprodcction. — T T ndeterminod. 



Mohave Yucca. 



Yucca r&ohavenste Sargent. 



DISTINGUISHING CHARACTERISTICS. 



The Mohave yucca has been known for about fifty years, but until about 

 eleven years ago it had been confounded with two other species, from which it 

 is now known to be distinct. Since its most extensive and characteristic growth 

 is found on the Mohave Desert, the common name here coined for it seems m ire 



"Considerable local use of the wood has recently been made for physician's splints. 

 The logs are pared into thin sheets. 



