238 MISCELLANEOUS CIRCULAR 92, U. S. DEPT. OF AGRICULTURE 



base common names on superficial, often fluctuating, resemblances 

 between botanically unrelated groups can only lead to confusion. 



There are limits, however, beyond which common names can not 

 follow botanical grouping. The botanical distinction of species may 

 be based on characteristics too minute or inconspicuous to be easily 

 recognized as the basis for distinct common names, as in the numerous 

 species and varieties of Basswood. Or an improper common name 

 may have become too firmly entrenched in usage to be upset, as, for 

 instance, the name Cedar applied to Juniperus, Chamaecyparis, 

 Thuja, and other genera. 



5. When botanical differences among species and varieties of a 

 genus are too slight to serve as a basis for distinctive common names, 

 a group common name should be applied. Examples are found in 

 the Basswoods, Willows, Hickories, Oaks, etc. 



Within certain genera there are groups of species having common 

 characteristics distinct enough to differentiate them as whole groups 

 from other groups within the same genus. Examples are the red 

 and white oak groups, the white and black ash groups, and the white 

 and yellow pine groups. These group distinctions should be preserved 

 in the names used for the individual members of each group, so far 

 as possible. 



It is natural and legitimate that group common names should be 

 more extensively used for lumber than ior the corresponding trees, 

 because the trees with their bark, foliage, flowers, and other character- 

 istics are often more readily distinguished than is the lumber cut 

 from them. 



6. Ordinarily a distinct generic common name should be used for 

 each member of a botanical genus, as Spruce (Picea), Pine (Pinus), 

 Oak (Quercus), Elm (Ulmus), etc., unless (a) firmly established 

 usage of the same common name for two or more genera (such as the 

 name cedar for Juniperus, Thuja, Chamaecyparis), or of two or more 

 generic common names for different members of the same genus (as 

 Butternut and Walnut for members of the genus Juglans), prevents 

 the adoption of the principle but does not lead to deception; or 

 unless (o) two or more genera are so closely related botanically and 

 their woods are so nearly identical in structures, properties, appear- 

 ance, value, and usefulness as to be to all intents and purposes the 

 same. This latter exception rarely applies to native woods, but con- 

 ceivably might apply to certain closely related woods of tropical 

 genera, if they are not readily distinguished in practice, and if no 

 deception results from the use of a group generic name. This prin- 

 ciple is simply an extension of the principle of the group common 

 name, as used in related species and varieties, to the larger groups 

 known as genera. It is recognized that generic classification is not 

 always fixed and unalterable, separate genera having sometimes been 

 combined into one genus and single genera having sometimes been 

 split up into tw T o or more genera. When practicable, however, it 

 would be preferable to follow the principle of a distinct name for each 

 genus. 



