266 OUTLINE OF PLANT GEOGRAPHY 



The forests of this region are made up mostly of trees of boreal 

 genera. Oaks in gnat variety, both evergreen and deciduous, are 

 especially abundant in these mountain forests, and several species 

 of pines and firs, a juniper and elder, are reminiscent of the forests 

 of Arizona and California. A species of Arbutus, much like the 

 California!! madrono is also found in the Mexican highlands. 



With the evergreen oaks, pines, and firs, there are deciduous 

 trees closely related to those of the temperate United States, such 



Xerophvtic vegetation, South Mexico, State of Michoacan. 

 Euphorbia (E. fuka). Photo., Mr. G. X. Collins. 



Cacti, 



as walnuts, sycamores, ashes and poplars, much like species found 

 in California and Arizona. 



Above the forest zone, on the higher mountains, the shrubs and 

 herbaceous plants are almost exclusively of northern types, grasses 

 and sedges, a great development of Compositae (Baccharis, Eupa- 

 torium, etc.), Ericaceae, Rosaceae, Umbelliferae and Cruciferae. 



The railway to the coast from Mexico to Vera Cruz passes 

 through the sub-tropical zone, "Tierra templada," into the tropical 

 zone, "Tierra caliente" reaching some 3,000 feet above the coast. 



As one descends, the oaks, pines, and other boreal genera be- 

 come mingled with trees of more tropical aspect, such as members 

 of the myrtle and custard-apple families, laurels, and especially 



