NOTES TO ACCOMPANY A VEGETATION MAP OF 
NORTHWEST MEXICO 
Introduction 
This paper embodies a preliminary study of the vege¬ 
tation of northwestern Mexico. Vegetation is here consid¬ 
ered to be the plant cover of an area in its general aspects 
of dominant associations and formations. The region des¬ 
ignated as northwestern Mexico comprises the Mexican 
states of Sonora, Sinaloa, Chihuahua, and Durango. These 
four states contain about 236,000 square miles, or a trifle 
less than a third of the republic’s total area. 
Botanical Collections 
The flora of northwestern Mexico has been compara¬ 
tively well studied. 1 The earliest descriptions of plants are 
to be found in the writings of Tello, Perez de Ribas, Obre- 
gon, and Pfefferkorn, and in the “Rudo Ensayo” and the 
“Relacion de la Nueva Mexico.” However, the area was 
untouched by trained botanists until the expedition of 
Charles II of Spain, which worked in Mexico under Dr. 
Martin Sesse from 1788 to 1804. Mo$ino, Castillo, and 
Longinos were the members of this expedition who made 
collections in northwestern Mexico. The chief result of this 
work was in the information given by Mogino to A. P. de 
Candolle while the former was a political exile in France. 
Von Humboldt and Bonpland stimulated scientific study in 
Mexico, but neither of them ever set foot in the northwest 
during their visit in 1803-1804. 
1. The chief bibliographies and histories of botanical research in Mexico are: 
Hemsley, W. B. Biologia Centrali-Americana ; Botany 4: 117-137, 316-332, London, 
1887. 
Leon, Nicholas. Biblioteca Botanico-Mexicana, Mexico, 1895. 
Harshberger, John. Phytogeographic Survey of North America, 30-33, 82-87, New 
York, 1911. 
Standley, P. C. “Trees and Shrubs of Mexico,” 9-19, Contributions from the U. S. 
National Herbarium, Vol. 23, Washington. 1920-1926. 
Just’s Botaniecher Jahreabericht, Leipzig, sporadic numbers on "Pflanzen-geo- 
graphie der Aussereuropaischen Lander.” 
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