INTRODUCTION. 



I 



13 



herbaceous 



i 



tlie summit ridge. Live cal^s grow upon the rocky sides of the ravines, and with them is 



frequently associated a species of cedar. Among the more interesting of the 



found here, are Dryopetdlon runcinatum, Vesicorim, and Colomicc. The narrow valley of the 



stream which runs through the bottom of the Pass is wooded with ash, cotton wood, and Mexican 

 sycamore. 



I 



VEGETATION OF THE UPPER VALLEYS OF SAN BERNADTNO, SAN PEDRO, AND SANTA CRUZ WITH THAT OF 



/ 



IHE ADJOINING MOUNTAIN RANGES. 



The country embraced in the ahove limits^ includes that portion of Northern Sonora, 



which divides the waters which flow north tov>^ards the Grila river from those whose course is 



south, towards the Gulf of Califoriiia. It is, as we have before stated, diversified with high 



wooded mountains and upland plains, well watered valleys and dry and barren tracts. The 



arborescent growth is not essentially different from that we have noticed in speaking of the 



^t^er divisions of country. Live oaks, the nut pine, cedar, ash, walnut and cotton wood are 



produced either upon the mountains or in the upland valleys. Its plains are covered with an 



uniform growth of upland grama grass, or in the more arid localities by mezc[uit and its thorny 



associates. This region furnishes a number of singular and highly interesting genera and 



species, most of which are described by Dr. Gray, in the second part of ^^Plantae Wrightiana?,'' 



in the Smithsonian Contributions. A reference to this work will give a better idea of the 



character and distribution of the flora of this district than our limits will allow us. As it 



occupies a station between several botanical divisions, so its flora partakes of that of those 



regions. The following list of some of the plants found here will be seen to embrace species 



belonging to California, Texas, Mexico, and New Mexico, viz : EschsclioUzia douglasiiy 



Zaiischneria Californica^ Eulohiis Cali/ornicus ^ Boivlesia teneray Anemone CaroliJiicma^ Draba 



I caroUnianaj Ccrydalis aurea, Androsace occidentalism Butosma texana^ Erodium texanum^ 



Layia Neo-mexicana ^ Cowania Mexicana. 



VEGETATION OF THE LOWER 



AND 



OE THE GILA. 



^ 



The region defined as above constitutes a very distinct botanical district, many of its peculiar 

 plants not being found elsewhere. As we have mentioned in a previous sketch, the valley of the 

 Santa Cruz, as it leaves the mountains in its northward course towards the Gila, gradually 

 looses its fertile character, and finally terminates in the desert plain which forms the table land 

 of the Gila. The vec^etation of this tract comprises many of the forms which are found on all 



the barren plains of the country. 



the 



Here, 

 Cacti 



elsewhere, the mezquit and 



There are 



the low arborescent Opuntias, generally bearing proliferous fruit, as well as several elliptic^ 

 stemmed species. The enormous EcMnocactus iDislizenii and Caespitose mammmarius and Cer 



i; 



common 



towers above all. A species of misletoe is common upon the mezquit trees of this region. 



The 



O 



localities we find Franaeria deltoidea, Enceliaft 



. 4 



