Volume I I Number 5 



The Plant World 



it TOagaztnr af (ftmi'nil ^kitanp 

 MAY, 1908 



ACROSS PAPAGUEKIA. 

 Daniel Trembly MacDougal. 



An immense Hattish ridge slopes from elevations ot 

 3000 to 4000 feet in southeastern Arizona, 300 miles west- 

 ward to the delta of the Colorado river and the upper part 

 of the Gulf of California. A score of mountain ranges 

 including the Whetstones, Santa Ritas, Santa Catalinas, 

 Tortolitas, Sierritas, Tucsons, Carobabis, Baboquiviris, Qui- 

 jotoas, Ajos, Growlers, Rincons, Dragoons, Mohawks, Gilas, 

 fulej, Lechuguillas, Maricopas, Ciprlanos, San Franciscos. 

 and San Rosarios, run transversely across the ridge with 

 crests that rise to over 9000 feet in some instances, the inter- 

 vening valleys being for the most part broad flattish troughs 

 with undeveloped drainage opening to the northward into 

 the Gila river and to the southward to the Altar and Sonoyta 

 rivers in Sonora. 



The area of several thousand square miles included, 

 might be properly termed the northernmost extension of the 

 desert which extends southward along the Pacific coast to 

 the Isthmus of Tehuantepec. The precipitation is less than 

 a dozen inches except on the higher summits, the greater part 

 of the yearly rainfall coming in midwinter and midsummer. 

 Temperatures of 118° and 120° F. have been recorded in the 

 lower levels, some places showing a daily maximum above 

 100° F, during portions of six months of every year. The 

 possible evaporation that would ensue from a water surface 

 would probably be between 80 and 100 inches per year, or 

 about six to eight times the precipitation. The general 



