Phytogeographie regions of North America. 345 
of the American continent as these influenced the distribution of plants. This 
gave a skeleton map on which to base subsequent research, which led to the 
completion of the map, as it finally appears. With the completion of the 
map in the rough, the unnecessary scaffolding, so to speak in the form of 
colored areas, lines and hachures were erased, leaving the finished chart, as 
a result of all the study that was put upon the distribution of North American 
plants in particular. The phyto-geographic map of Mexico was submitted to 
Dr. J. N. Rose of the U. S. National Museum and Mr. Cyrus G. PRINGLE of 
the University of Vermont, whose invaluable criticisms were used in mapping 
the distribution of Mexican plants. The boundaries of the phyto-geographic 
zones, zone-sections and regions will be given in connection with a description 
of each area, and the reasons for the delimination of these districts have been 
given in a foregoing chapter III, p. 203—3 11. 
