(322) 
In addition to the species common to both deserts the following 
are found only in the Colorado Desert: 
Neowashingtonia filamentosa Olneya Tesota 
Nolina Parry Condalia Parryt 
Prosopis velutina Foquierta splendens 
Acacia Greggii Ramona Vaseyi 
Parkinsonia aculeata Beloperone californica 
Parkinsonia microphylla Gaertneria tlicifolia 
Cercidium Torreyana Coleosanthus frutescens 
Krameria Gray Gutierrezia bracteata 
Parosela Emoryt Ericameria brachylepis 
Parosela Schotti Baccharis sarothroides 
Parosela spinosa Encelia farinosa 
A study of the geographical distribution of the species not 
common to both deserts shows that the Mohave Desert species 
are of the Great Basin element, most of them being common to 
southern Nevada, southern Utah and northern Arizona, and 
that the species restricted to the Colorado Desert are of southern 
origin, and extend into Lower California, southwestern Arizona 
and northwestern Sonora. 
EXPLANATION OF PLATES 
Pirate A 
Relief map of California, from the original model by N. F. Drake. Pub- 
lished through the courtesy of the Department of Geology of Leland Stanford 
Jr. University. 
Pirate B 
Dry Lake, San Bernardino Mountains, altitude 3180 meters, showing a 
pure forest of Pinus Murrayana and Pinus flexilis. Canadian Zone. 
PLatTeE C 
Juniperus occidentalis, Bear Valley, San Bernardino Mountains, altitude 
2230 meters. Transition Zone. 
Puate D 
Open park-like forest of Pinus ponderosa Jeffreyt, Mount Pinos, altitude 
2300 meters. Transition Zone. 
PuaTe E 
Pseudotsuga macrocarpa intermingling with the chaparral, Topatopa 
Mountains, altitude 1800 meters. Upper Austral Zone. 
Piate F 
Alnus hombifolia, Waterman Canyon, San Bernardino Mountains, alti- 
tude about 1200 meters. Upper Austral Zone. 
