10 BULLETIN" 728, TJ. S. DEPARTMENT OF AGRICULTURE. 



Key to the species of yucca. 



I. Leaves quite numerous in the head, narrow, one-half inch wide or generally- 



less, with a thin, white, threadlike filament on the margin; fruit a 

 dry pod that bursts. 



1. Mature plant with a trunk from a few inches to several feet in length; 



flower stalk 5 to 10 feet high and much branched 



1. Yucca elata. Soap weed, palmilla, ooce. 



2. Mature plant usually without any perceptible trunk; stem, if any, 



at most only 6 or 8 inches high; leaves usually less than 2 feet long; 

 flower stalk never over 3 or 4 -feet high, usually sparingly branched. 



2. Yucca glauca. Bear-grass (in eastern New Mexico). 



II. Leaves less numerous, quite stiff, broad, \\ to 2 inches wide, one-eighth 



to one fourth of an inch thick, with coarse woody threads on the 

 margin; fruit more or less fleshy, at least when young. All species 

 called Spanish bayonet, or dagger. 



1. Mature plant with short trunk (a few inches high) or none, fruit large, 



5 or 6 inches long, and fleshy 3. Yucca baccata. Amole, datil, dagger. 



2. Mature plant with trunk several feet in height; fruit smaller, 3 to 4 



inches long, fleshy at first, but drying up without bursting 



4. Yucca macrocar pa. 1 Palma, dagger. 



III. Leaves intermediate in width and rigidity between the other two 



groups, margin not bearing a thread, but, being horny and with very 

 minute teeth, is barely visible to the naked eye; fruit a dry pod that 

 bursts open 5. Yucca rupicola. 2 



OTHER PLANTS AVAILABLE. 



Besides the above-named plants there are several others that could 

 doubtless be used in the same manner with equally good results. The 

 Joshua tree (Clistoyucca arborescens) of the Nevada-California desert 

 region (also called quiote by Spanish-speaking people), Hesperoyucca 

 whipplei of the California coast region, and Hesperaloe parviflora of 

 Texas east of Del Rio could be used wherever they occur in sufficient 

 abundance. Samuela faxoniana of the Sierra Blanca region in Texas 

 will probably be used along with the other plants that are available 

 there, and they are already beginning to be used. These all look like 

 yuccas and at one time or another have been considered to be yuccas. 



DISTRIBUTION AND DENSITY. 



The diagrammatic map (fig. 1) shows the regions in which the more 

 important species occur. Each has its own soil, altitude, and expo- 



1 This is the commonest species of this type in the region from Douglas, Ariz., to Marfa, Tex. Yucca 

 mohavensis is another very similar species that grows in the Mojave Desert region of northwestern Arizona, 

 southern Nevada, and southeastern California. Yucca brevifolia and Yucca schottii occur in the foothills 

 of southern Arizona. Yucca treculeana occurs in the lower Rio Grande region from Laredo southward. 

 None of these are ever very abundant, but all of them could doubtless be used for the purpose under dis- 

 cussion. 



2 Two other species, Yucca thompsoniana and Yucca reverchoni, occur associated with this species in 

 I he region from Haywood, Tex., north to San Angelo and eastward on rough hillsides along with sotol and 

 sacahuista. 



