Sinaloan District. 637 
vegetation is perennial and of slow growth, stunted in aspect. It is not distri- 
buted uniformly, but arranged in separate tufts or clumps, gathering into a 
nearly continuous mantle in wetter spots. The arborescent vegetation 
is of two types, viz., (1) trees and shrubs allied to those of humid lands, but 
morlified to fit arid conditions; and (2) distinctive forms, evidently the result 
of desert conditions. The prevailing tree is Prosopis julifiora which on the 
alluvial fan of the Rio Sonora grows with remarkable luxuriance, dominating 
elsewhere the plains and pushing well up into the canyons. Associated 
with it are Olneya tesota, Acacia Greggüi and on Tiburon Island in similar 
associations occurs Parkinsonia Torreyana. The ocotilla Fouguiera splendens is 
“also abundant in all places, except rocky slopes, while the higher plain slopes 
show such pulpy stemmed shrubs as Jatropha cardiophylla, F. spathulata and 
Bursera microphylla. 
Along the lower stretches of certain rivers grow Guasacum Coulteri and 
Facguinia pungens with Caesalpinia gracilis on the flanks of gorges in the 
shelter of more vigorous shrubs, as likewise Sebastiana bilocularıs. The lower 
extremities of sand washes, wet only in times of flood, are characterized by 
Hymenoclea monogyra which shrinks to stunted tussocks after a year or more 
of drought. Phragmites communis forms cane brakes also here about all per- 
manent waters'). 
The coasts of Sonora both insular and mainland are skirted by strips of 
shrubbery maintained by fog moisture. Along the mountainous parts of the 
coast the strip is narrow and indefinite, but on the plains, it extends inland 
for several miles. Celtis pallida, Maytenus phyllanthoides and Frankenia Pal- 
meri are characteristic shrubs. Cereus (Pachycereus) Pecten aboriginum (see 
Fig. 9 p. 297), Zarrea (Covillea) are found in the neighborhood of Guaymas. 
The salt waters of Guaymas Harbor and other bays along the coast are 
see colored map) and Avicennia nitida 
Thurberi and C. (Pachycereus) 
The mountain sides near the Gulf of Californi 
diana with which is associated Ficus Palmeri spri 
along rocky barrancas near a permanent water supply. 
spreading over the intervening spaces particularly in th 
shrubs of the genera Cassia, Microrhamnus, Celtis, Randia, Stegnosperma, Krameris, Erankenia 
| ied by Larrea. Various eaeti are inter- 
mixed with the above plants viz., Cereus giganteus, C. Pringlei, C. Thurberi, C. Sehottil, Echinet 
{ : 31-36. 
1) Mc Ger, W. J.: The Seri Indians, 17th Report, U. S. Bureau y men 
2) Since this book went to press, there has been R = e Kakteen (1899); 
by American botanists, compare SCHUMANN, KARL: Gesamtbeschreibung der i Er 
BERGER, 16th Rep. Mo. Bot. Gard.; BRITTON, N. L. gegen 
i # i & of north- 
North America, Contr. U. S. Natl. Herb. XU: 413437; he 3 nis 
eastern and central Mexico (illustrated), Annual Report Bmishsonain Insetue "9° 
