240 LEQUMINOSAE 



feet liigh whoso trunk .liiuneter at 18 iiu'lu-s above tlic gnniiHl was 2 feet and i;, inch. Fence 

 posts arc made from the timber and if charred on the outside are said not to be attacked by 

 boring beetles. Because the tree is long-lived and has a dense linc-grained wood it is chosen as 

 a "bearing" tree by land surveyors. For fuel in the desert it forms a constant resource for the 

 settlers. It is especiallv i>rized for branding-iron fires, because it holds heat so well. Sub- 

 axillary to the stout thorns on the brandilets are developed abbreviated branchlets or spurs 

 roughlv similar to those of Prunus armeiiiaca (Apricot) or Ginkgo biloba. 



Field note.— In a good season the abundance of straw-yellow llowers transforms the appear- 

 ance of the tree. The honey gathered by the honey l>ee is line, clear and delicious, hence "Honey 

 Mesquite.'' The flowering season is usually long and a tree may set fruit two or three times in 

 the course of the long summer. Each raceme with its numerous flowers matures only about 1 to 

 4 fruits, though sometimes as many as 18, the pods having a tendency to set on one side of the axis. 

 The most interesting and useful tree of the desert, its sweet nutritious pods are greedily eaten by 

 animals and even in their natural state serve man if he be not too delicate. When ground, how- 

 ever, the fruit is highly valued. E. L. Greene, during his journey in 1880 across the Colorado 

 Desert writes: "the mesquite meal which Indians and Mexicans manufacture by drying and 

 grinding these pods and their contents, is perhaps the most nutritious bread-stuff in use amongst 

 any people'' (Am. Nat. 15:30). In the overflowed lowlands in the Palo Verde Valley along the 

 Colorado Eivcr considerable quantities of the beans are still harvested each year by the Indians 

 who sell the pods to the settlers for winter cattle feed. They are also an important source of food 

 for skunks, bobcats and coyotes, especially in the Colorado Kiver bottoms. Individual trees are 

 often infested by the Desert Mistletoe (Phoradendron calif ornicum Nutt.) and not infrequently 

 die as a result of the attack of the parasite. 



The tree is an almost infallible sign of water, either on the surface or at varying distances 

 below. Furnace Creek wash, after leaving its canon in the Funeral Mts., has built up a great 

 detrital fan on the floor of Death Valley, forming a half-moon about five miles across. The base 

 of the fan is rubble, but outside this is a zone of finer sandy sediment. On this sediment zone 

 occurs the Honey Mesquite, forming thus a great semicircle extending from the base of the foot- 

 hills south of the entrance to Furnace Canon out over the floor of the valley in a curving band 

 one-half mile wide, returning again to the base of the foothills north of the canon ( Jepson Field 

 Book, 33:121, — 1917, ms.). Clumps of the bushes mark also the water-bearing stratum in the 

 foothills of the Funeral Mts., near the Furnace Creek ranch in Death Valley. 



The sprawling habit of the tree acts as a break to wind-bloAvn sand and a dune often forms 

 about an mdividual. Bounded sand dunes, 10 to 20 feet liigh and two to three times as broad, 

 with the branches of a tree protruding from the periphery, form a feature of the flats in the 

 Coachella Valley and in Death Valley. As the branches continue to lengthen the dune increases 

 in size, so that a tree, in the course of time, is very deeply buried with only the tips of the crown 

 protruding. 



Locs. — Upper San Joaquin Valley: Buena Vista Lake, F. M. Anderson. Eastern Inyo Co.: 

 Panamint Valley ; Emigrant Sprs., Jepson ; Furnace Creek Ranch, Death Valley, Jepson ; Eagle 

 Sprs., Death Valley, Jepson 6948a; Tecopa, Jepson. Mohave Desert: Ijfiinaster (15 mi. e.), 

 Peirson; Barstow, Jepson 4790; Box S Spr., J. T. Howell 2688; Warrens Well, e. of :Morongo 

 Valley, J. T. Howell; Cronese Valley, Jepson; Needles, Jepson 5483; Little Chemehuevis Valley, 

 Colorado River, Jepson 5211. Colorado Desert: Riversir'e Mts., Jepson; Cottonwood Spr., Cot- 

 tonwood Mts., Jepson; Twenty-nine Palms, Jepson; Tndio, Jepson; Palm Caiion of San Jacinto, 

 Jepson 1378; Borrego Valley, Jepson 8816; Collins Valley, Jepson; Sentenac Valley, below San 

 Felipe Valley, Jepson; Harper Well, Jepson; Vallecito, e. San Diego Co., Jepson; Holtville, 

 plain e., Jepson; Alamo River, e. of Calexico, Paiish 8297. Coastal S. Cal.: San Bernardino, 

 Parish; San Jacinto Lake; Aguanga, Jepson; Temecula, Parish; San Diego (Zoe 4:342). 



Eefs. — Prosopis jvlifloka DC. Prod. 2:447 (1825), type from s. Jamaica. Var. glandu- 

 LOSA Ckll. Bull. Agri. Exp. Sta. N. Mex. 15:58 (1895); Jepson, Man. 513, fig. 513 (1925). 

 P. gJandulosa Torr. Ann. Lye. N. York 2:192, pi. 2 (1828), type loc. "on the Canadian?", James. 



2. P. pubescens Bentli. Screw-bean Mesquite. Slirub or small tree 10 to 35 

 feet high, with narrow crown and ascending: branches; branches armed with stont 

 often whitish stipnlar spines 2 to 6 lines long ; leaves canescently puberulent ; leaf- 

 lets oblong, 1 to 5 lines long ; flowers 2 lines long, borne in spikes 2 to 3 inches long, 

 each spike setting 2 to 15 pods ; petals connivent % way up into a tube ; pods coiled 

 into a narrow straight cylindric body 1 to l^A inches long; seeds less than 1 line 

 long. 



Sandy or gravelly washes or ravines, 200 to 2500 feet : Colorado and Mohave 

 deserts ; north to Death Valley. East to New IMexieo. July. 



Field note. — The trees, mostly 10 to 18 feet high, exhibit a single erect trunk or several such, 

 the brownish bark on the main stem becoming stringy. W^hen cut for fuel, for which purpose it 

 is accounted rather inferior, the tree regenerates by crown-sprouts. Along the Mohave River, as 



