Herbarium specimens have been an important source in 
preparation of the maps of minor western hardwoods. During a 
period of several years the compiler visited herbaria in 15 of the 
17 States, mostly at universities. In 12 States he copied locality 
records from specimen labels in one herbarium, sometimes 
more. 
Some State herbaria maintain unpublished card files of maps 
showing by dots where herbarium specimens were collected, 
either by counties or localities. In these six States, species maps 
with locality records of specimens kindly were made available or 
were compiled by the curators, as follows: North Dakota, O. A. 
Stevens: South Dakota, Theodore van Bruggen: Wyoming, John 
R. Reeder: Colorado, Robert P. Adams: New Mexico, William 
C. Martin: and Texas (incomplete), Billie L. Turner. Ronald L. 
McGregor provided numerous county range extensions from his 
forthcoming atlas of plants of the plains region. George W. 
Argus has assisted in the willow genus (Salix). Credit is due all 
curators for the privilege of consulting the herbaria and for their 
cooperation in supplying these records. 
Similar records from publications, herbarium specimens, and 
maps have been obtained for distribution outside the United 
States. For Canada, the compiler consulted herbaria in Victoria, 
Vancouver, and Ottawa. Special acknowledgment is made for 
copies of unpublished maps, as follows: British Columbia, T. C. 
Brayshaw: Northwest Territories, W. J. Cody and A. E. Porsild. 
For Quebec the species maps and notes in the thesis by Camille 
Rousseau (1974) were especially helpful. The manuscript “Flora 
of Canada” by H. J. Scoggan, not yet published, was examined 
for valuable information on the distribution and northernmost 
records. 
The compiler visited Herbario Nacional, Instituto de Biologia, 
Universidad Nacional Aut6énoma de México in Mexico City, to 
copy locality records of specimens in that country. The flora of 
the region of the Rio de Bavispe in northeastern Sonora (White 
1948) near the border cited detailed localities of many species. 
Further information for many species was copied from speci- 
mens at the United States National Herbarium (US), of the 
National Museum of Natural History in Washington, D.C. That 
herbarium contains important collections from Mexico which 
served in the preparation of “Trees and Shrubs of Mexico” 
(Standley 1920-26). Many Mexican extensions have been con- 
tributed by Jerzy Rzedowski (general), Raymond M. Turner 
(Sonora), and Reid V. Moran (Baja California). Ranges and 
southern limits of some species in Mexico are less definite than 
northward because of fewer available specimens. 
Additional records were available in the Forest Service. The 
unpublished maps compiled by George B. Sudworth have been 
reexamined for old records such as observations by foresters. 
Charles Feddema, curator of the Forest Service Herbarium 
(USFS), kindly has compiled locality records for many species. 
That herbarium has perhaps the largest number of specimens 
from the western National Forests. 
Maps of vegetation, forest types, topography, and landforms 
have been very helpful in determination of lines along the 
borders of ranges. In the Western States, sharp limits of forests 
and climatic zones of vegetation are based largely upon 
differences in altitude. Regrettably, maps of the same region 
sometimes differ in their classifications and type boundaries. 
Forest type maps in color have been issued by the Forest 
Survey of the Forest Service for nearly all forested parts of the 
country in many scattered publications, mostly on the forest 
resources of one State or smaller unit. Detailed vegetation maps 
have been published for a number of States. 
In this Atlas volume the main source of vegetation boundaries 
has been the map Vegetation by A. W. Kichler, National Atlas 
Sheet No. 90 (U.S. Geological Survey 1970). This detailed, 
highly accurate map was reduced in size from a separately 
published one on the vegetation of conterminous United States 
with explanatory text (Kiichler 1964). The map Forest Types. 
National Atlas Sheet No. 182, prepared by the Forest Service, 
has been useful and was reduced and adapted slightly for 
inclusion in the first volume as an overlay (overlay map 9, Major 
Forest Types). 
Reduced or small-scale maps naturally do not show local 
variations of vegetation and plant distribution in detail. For 
example, a few small, isolated mountains with outlying stations 
for certain species have been omitted both from vegetation 
maps and from this Atlas. Further local occurrences may be 
indicated by the State vegetation maps printed at larger scales. 
The compiler has had field experience in many parts of 
Western United States, including Alaska, also in Mexico. 
During 8 years, 1934 to 1941, he was in research work as 
assistant and associate forest ecologist in Arizona and New 
Mexico. Afterwards he prepared “Southwestern Trees, a Guide 
to the Native Species of Arizona and New Mexico” (Little 1950). 
Earlier, he was a student, teacher, and research worker in 
Oklahoma, also graduate student in Utah. Much information on 
landforms and vegetation has been obtained on field trips in 
various parts of the country, also from airplane and car windows 
across the different States. 
These maps have been prepared through the years along with 
other work by the compiler and an assistant. Sources of most 
locality records were indicated on the working maps and could 
be traced if necessary. However, detailed record keeping and 
reproduction of hundreds of dots on most maps (such as by 
computers) would have added greatly to the time and cost of 
preparation without increasing the accuracy and would have 
delayed publication. 
For assistance in preparation of the maps, credit is due 
Barbara H. Honkala, research botanist, who also made the 
cover design and the base maps, and Kathy M. Robinson. The 
final maps were drafted by Ziya K. Akalin, engineering 
draftsman. 
EXPLANATION OF THE MAPS 
Species maps of Volume 3 follow the general plan of Volume 
1, from which this explanation is adapted and slightly con- 
densed. However, like Volume 2, the page size has been 
reduced slightly to 914 by 1134 inches. The obvious advantages 
include lower costs and prices, less weight, and greater 
convenience in handling and storing. The scale of the base 
maps of the United States remains the same in these volumes, 
1:10,000,000. Thus, the maps can be compared readily. Also, 
the nine transparent overlays from Volume 1 can be adapted to 
Volumes 3 and 4, which have no overlays. The vast size of 
Alaska, more than twice that of the second largest State, is 
clearly emphasized in Volume 2, on the same scale, 
1:10,000,000. 
As in Volume 1, two base maps are used as needed for the 
210 tree species in Volume 3, one of the United States for all 
(except 2 from Alaska) and another of North America for 62. 
These base maps have no lettering. However, place names are 
given on two additional base maps inserted for reference. Base 
