This check list aims to compile scientific names and current synonyms, approved common names and others in use, and ranges of the native and naturalized trees of the United States of America (including Alaska). It is primarily a reference for foresters, botanists, students, and all others interested in trees. One of its important objects is to encourage uniform usage of names for tees. The third in a series, this is the official standard for tree names in the Forest Service. The trees of the United States (genera, species, varieties, and hybrids) are listed in a a single alphabetical order under accepted scientific names in boldface, instead of by families. Following the the alphabetical check list is the list of Commercial Names for Lumber. Index of Common Names is also included.