Weight of Seasoned Wood in Pounds per Cubic Foot. 32. Modulus of Elasticity. Modulus of Rupture. Remarks. The largest of the United States Palms. Much used for landscape effects in California. [p188] YUCCA. (_Yucca_.) The eighteen species constituting this genus are all American. Twelve of them are found in the southern and western United States, and eight of these are mentioned by Sudworth[114] as arborescent. Several of the Yuccas are cultivated because of their beautiful lily-like flowers. The Tree Yucca or Joshua-tree affords wood. This last named species produces a short stout trunk, peculiar in that it is covered by thick bark. The soft, spongy wood is sometimes sawn into lumber, made into souvenirs and lately into artificial limbs. An attempt to manufacture it into paper-pulp[115] is said to have failed because of high cost made necessary by the remote position of the industry. Hough notes[116] that trees are sometimes attacked by borers that impregnate the walls of their tunnels with hardening antiseptic solutions, causing such parts to remain after the disappearance of the others. And that these parts are described as "petrified wood," and are prized for fuel since they burn with "little smoke and great heat." The eight species noted by Sudworth are as follows: Yucca arborescens (Joshua tree). Yucca treculeana (Spanish Bayonet). Yucca gloriosa (Spanish Dagger). Yucca mohavensis (Mohave Yucca). Yucca aloifolia (Aloë-leaf Yucca). Yucca macrocarpa (Broadfruit Yucca). Yucca brevifolia (Schott Yucca). Yucca constricta. [p189] FOOTNOTES [Footnote 114: "Check List," U. S. Forestry Bul. No. 17.] [Footnote 115: South of Mohave Desert in California about twenty years ago.] [Footnote 116: American Woods, Part VII, p. 57.] [Illustration: PLATE 38. YUCCA (_Yucca arborescens_). _By courtesy of Messrs. Doubleday, Page & Co. Photograph by Conaway._ Wood of Yucca.] JOSHUA-TREE, YUCCA. _Yucca brevifolia Engel._ _Yucca arborescens Torr._ Nomenclature. (Sudworth.) Joshua-tree, The Joshua, Yucca, Yucca Tree (Utah, Ariz., N. M., Cal.). Yucca Cactus (Cal.). Locality. Central and lower Rocky Mountain region. Features of Tree. Twenty-five to forty feet in height, six inches to two feet in diameter. Thick outer cover or bark.[117] Color, Appearance, or Grain of Wood. Light brown to white, porous grain. Structural Qualities of Wood. Light, soft, spongy, flexible in thin sheets. Representative Uses of Wood. Paper-pulp, souvenirs, boxes, book covers, and other small articles. Weight of Seasoned Wood in Pounds per Cubic Foot. 23. Modulus of Elasticity. Modulus of Rupture. Remarks. Bark is unusual in the case of endogenous trees. Arborescens refers to fact that _it_ is a tree. [p190] FOOTNOTE [Footnote 117: See paragraph Bark, Endogenous Trees, page 55.] BAMBOO. (_Bambusæ_.)