ACROSS PAPAGUBRIA 



95 



section from southeast to northwest across this region, the 

 material collected including many new species, but so far, 

 no opportunity has been offered for any attempt at an 

 interpretation of the general features of the vegetation, in- 

 cluding its origin, distributional movements and environ- 

 mental relations. 



As an attempt to secure information upon some of these 

 points an expedition was organized at the Desert Laborator}^ 

 in November, 1907, which crossed the entire width of 

 Papagueria from east to west. The route traversed the 



FIG. 1. — l^iagraniiiiatie map oi ir'apagueiia. 



mountain passes and crossed the broad ^•alleys west from 

 Tucson for a distance of 125 miles, then made southward 

 in the Ajo valley to the streamway of the Sonoyta river 

 below the international boundary. Here the old trail or 

 Devil's Road was followed down the curving river to the 

 disappearance of the water in the sands, thence westward 

 across the plains to the Pule desert and southward to the 



