i 9 o 4 ] MAC DOUGAL- DELTA AND DESERT VEGETATION 45 



ary across a typical portion of the desert mesa was the route followed 

 by Mexican prospectors rushing to the Californian gold fields in 

 1849, and in the waterless stretch of i50 km between Quitovaquito 

 and Tinajas Altas may be counted over four hundred small circles 

 and crosses of loose stones by the side of the trail, grim evidences of 

 failures to negotiate this formidable "Jornada del Muerto." 



Attempts to penetrate the desert directly from the coast have met 

 with equally serious difficulties. The shore is fringed with mud flats 

 many kilometers in width, and numerous sand bars bare at low 

 water; the tides rise 4-io m and produce currents that run 4-8 km per 

 hour, forming waves or bores that sweep up the river, at times endan- 

 gering all craft not in protected anchorages. But few sheltered anchor- 

 ages are to be found in the upper Gulf, and nearly all of these are far 

 from a supply of fresh water. The few expeditions to this region in 

 which attention was paid to the flora are easily recounted. 



Colonel Andrew B. Gray traversed the desert from the inter- 

 national boundary to Adair Bay in 1854, discovering the singular 

 parasitic Ammobroma Sonorae Torr., 2 which fastens to the roots of 

 Franseria and Dalea at depths of 60-1 20 cm in the sand, and sends 

 its fleshy stems to the surface, on which the flowers appear to rest. 



Dr. E. Palmer traveled southward from Yuma to Lerdo near the 

 head of tidewater in 1889, and collected about two dozen species of 

 plants, 3 but no general account of the expedition is available. 



Descriptions of a number of the plants are to be found 'in the 

 accounts of the boundary survey, 4 in which but little attention, 

 however, appears to have been paid to the flora of the delta. 



T. S. Brandegee 5 made a long journey overland, in the same 

 year in which he traversed Baja California, for a distance of several 

 hundred miles northward to San Quintin in about the same lati- 

 tude as the southernmost point reached by my own expedition. How- 

 ever, he did not reach the country east of the main divide north of 

 San Luis Bay, 30o km south of the mouth of the river. 



2 Torrey, J., Ammobroma, a new genus of plants. Ann. Lye. Nat. Hist. N. Y. 

 8: June r864. 



3 Rose, J. N., Contrib. U. S. Nat. Herb. 1:27. 1890. 



4 Report on U. S. and Mex. Boundary Survey, Emory 2:21. 1859. 



5 Brandegee, T. S., A collection of plants from Baja California, 1889. Proc. 

 Calif. Acad. II. 2:—. 1889. 



