HITCHCOCK AND CHASE — NORTH AMERICAN PANICUM. 7 



spellings are not given formal standing as synonyms, but are listed 

 under the proper* paragraph — that is, in this case, under Panicum 

 barbulatum. 



SPECIES, SUBSPECIES, AND FORMS. 



The determination of the relation of taxonomic groups rests, in the 

 last analysis, upon judgment and experience. Such judgment is 

 greatly influenced by the amount of material that has been examined, 

 both in the herbarium and in the field. Our judgment concerning the 

 taxonomic rank of many of the less known groups may be altered 

 after an examination of more specimens. The herbarium may show 

 only 1 per cent of specimens intermediate between two groups, while 

 a study of the same groups in the field may show a much larger pro- 

 portion of intergrades. Or, field work may show, on the other hand, 

 that the peculiar or intermediate specimens are rare and that the two 

 groups are easily distinguished. The line is not sharp between forms 

 and subspecies nor between subspecies and species. If a group of 

 specimens presents constant characters of what we consider major 

 importance, it is recognized as representing a species. If the charac- 

 ters are of minor importance, but constant and well marked, and the 

 specimens tend to show a distinct geographical range, the group may 

 still be given the rank of a species. If two groups present fairly well 

 marked characters, but there is a considerable proportion of interme- 

 diate specimens — that is, the characters are not constant for the two 

 groups — they stand in the relation of species and subspecies. The 

 names species and subspecies are a taxonomic convenience and are 

 entirely arbitrary. They may not represent a biological relation in 

 the sense that one is an offshoot or development from the other, but 

 signify only that the form to which the name species was applied was 

 recognized and given taxonomic or nomenclatorial standing before 

 the other. The species may be the less common or a product of local 

 conditions. Panicum huacJtucae is the name applied originally to a 

 specimen from the Huachuca Mountains, Arizona, but represents an 

 outlying form of a widespread species. The commoner form has been 

 designated a subspecies, P. JiuacJiucae silvicola, because the name was 

 applied to this at a later date. 



On the other hand, the fact that there are occasional intermediate 

 specimens does not, of itself, invalidate the standing of two related 

 groups as species. It becomes then both a question of fact and a 

 question of judgment. If the two groups as a whole show well-marked 

 and fairly constant characters, and an examination of a large number 

 of specimens indicates that as a matter of fact the number of inter- 

 grades is comparatively few, we have accepted the two groups as 

 species and have mentioned intermediate herbarium specimens. 



