LILIAGEAE 



SoAPTREE Yucca. Spanish-bayonet 

 Yucca elata Engelm. 



HABIT. A tree often 1 5-20 feet high and 7-8 inches in diameter 

 with a deep, branched, underground stem; simple or branched 

 at top; covered with pendent, persistent dead leaves. 



LEAVES. Alternate; simple; 20-30 inches long and !4-k2 

 inch wide ; thin and flat above, rounded below ; glabrous ; yellow- 

 green; entire pale margins soon splitting into slender filaments; 

 parallel-veined; persistent; stipules absent, 



FLOWERS. Regular; in compound, terminal panicles, 4—6 

 feet high; perianth cup-shaped, white, 3^/2-4 inches across; 

 stamens 6; ovary 6-sided, 3-celled; ovules numerous. 



FRUIT. Erect, oblong capsule, 1^-2 inches long; 3-valved; 

 light brown, thin and woody outside; light yellow inside; edible. 

 Seed: numerous, black, Yi inch wide. 



BARK. Dark brown; with thin plates; H inch thick. 



WOOD. Light; soft; spongy; pale brown or yellow; in con- 

 centric layers. 



SILVICAL CHARACTERS. Lower Sonoran zone; intolerant; 

 on desert plateaus; large roots used as substitute for soap. 



Seven species of Yucca reach tree size: 

 1. Southwestern. 



2. Fruit erect, dehiscent; flower clusters long-stalked; leaves fila- 



mentose/thin, pale yellow-green Y. elata-. 



2. Fruit pendent, indehiscent; flower clusters sessile or short-stalked; 

 leaves concave above the middle. 



3. Fruit with thin, dry flesh; leaves blue-green, serrate; south- 

 western Utah to California Y. brevifolia Engelm. ; Joshua-tree 

 3. Fruit with succulent flesh; leaves with no, or minute teeth. 

 4. Panicle hoary-tomentose; leaves flexible, 2^—3 feet long; 



margins not filamentous ; southern Arizona 



Y. schottii Engelm.; Schotts Yucca 



4. Panicle glabrous or puberulous; margins filamentous. 

 5. Leaves 2^-4 feet long, dark green; Texas. 



6. Leaves concave ; perianth nearly free 



Y. treculeana Carr. ; Trecul Yucca 



6. Leaves flat, perianth united into tube 



Y. faxoniana Sarg. ; Faxon Yucca 



5. Leaves 1 ^-2 feet long, light yellow-green. 



7. Style elongated; western Texas to eastern Arizona. . . . 

 4. Y. torreyi Shaf. ; Torrey Yucca 



7. Style short; southeastern Nevada, northwestern 



Arizona 5. Y. mohavensis Sarg.; Mohave Yucca 



1. Southeastern Coastal Plain, North Carolina and south. 



8. Leaves sharply serrate on horny margin; fruit succulent 



Y. aloifolia L., Aloe Yucca 



8. Leaves entire or nearly so; fruit with thin dry flesh 



Y. gloriosa L. ; Moundilly Yucca 



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