Great Basin: Mohave District. 585 
geographic anomaly. Here Pinus sabiniana, Quercus Douglasii and ©. Wis- 
lizeni, trees of the western slope of the Sierra Nevada throughout central Cali- 
fornia, come through Tejon Pass and the unusual sight is presented of foot 
hills clothed with an almost unmixed growth of scrub oaks. Here too are 
found Aesculus californica, Balsamorrhisa deltoides, Gilia tricolor, Layia 
heterotricha and Collinsia Torreyi which have enterid through the same gap 
to the eastern deserts. 
The western or elevated part of the Mohave Desert is noted for Yucca 
arborescens and in places this tree is associated with Juniperus californica. 
Eastward the juniper ends and the creosote bush Zarrea mexicana appears 
and in lower levels becomes except in the wash, the prevailing bush. 
The BUETHRAFEEEN element, which preponderates over the southeastern, consists of such 
genera as: Actinella, Amsonia, Atrichoseris, | Cleomella, Eurotia, Forestiera, Glossope- 
talon (Forsellesia), a Kochia, Lygodesmia, Monoptilon, re ren (= Kunzia), 
Stanleya, Salazaria trichopappus while a southeastern ele omprises a few 
genera: Canotia, a Fallugia, Psilactis?), ‘The northeastern genera are ae which extend 
into Nevada, Utah and the Great Basin, and southeastern genera are those whose range is into 
Arizona, or into northern Mexico. 
1. The lower Desert Formations. 
Larrea Belt. The most generally distributed shrub of this desert is Larrea 
Mexicana (= Covillea tridentata), ascending from the lowest elevation that of 
Death Valley to about 1500 meters on the mountains. Associated with it at 
about the same elevation grows Franseria (Gaertneria) dumosa. The upper 
limit of this belt which MERRIAM calls the *Lower Sonoran Zone”, is only 
a little below the lower limit of timber. 
Mesa Formation. Larrea and Franseria are the commonest shrubs of the 
mesas, but at various localities some one or more of the following species are 
often abundant according to COVILLE’?). 
Acamptopappus sphaerocephalus, Amphiochyris Fremontii, \Aster mohavensis, Atriplex con- 
fertifolia, A. hymenelytra, BEDEN an var. u ee armata, Cereus Engelmanni, Echino- 
eactus polycephalus, Opuntia basilaris, O. echinocarpa, Ephedra californica, Hymenoclea 
salsola, Krameria parvifolia, ar Andersoni, Saar mexicana, Tetradymia comosa, Yucca 
arborescens, Y. macrocarpa. — Some of these plants are confined to the upper aRundeN of 
this belt, viz: Acamptopappus toner Aster meter Yucca AT Hyme- 
noclea salsola and Lycium Andersoni are common throughout it. The perennials common on 
the mesas are Euphorbia polycarpa, Cilodhrlk oblongifolia, Lenin Fremontii and Feige 
laevis, while as annuals occur Leptosyne a ii, Plantago patagonica var. gna des (= P. 
Purshü), Sisymbrium canescens, Gilia floccosa, ' Chorizanthe rigida, ler“, obtusifolia, Esch- 
scholtzia minutiflora, Encelia eriocephala, Atrichoseri platyphylla. 
Canyon Rocky Slope and Sandhill Formations. Growing in the shade of 
rocks or in their crevices in the canyons, in the coarse pebbly plains and on 
the dry sandy hills may be BRMEMBEER the following associations. 
1) PARISH, S. B.: loc. cit. see also page 289— 293. 
2) CoviLLe, F. V.: Botany of the Death Valley RER: Contributions U. S. National 
Herbarium IV: 2ı. Washington, 1893. 
