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 huachucae is the name applied originally to a 
specimen from the Huachuca Mountains, Arizona, but represents an 
outlyimg form of a widespread species. The commoner form has been 
designated a subspecies, P. huachucae 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. 
