250 
PACIFIC SCIENCE, Vol. IV, July, 1950 
in taxonomy is adding much valuable in- 
formation to the field. No worker can afford 
to ignore this work. However, taxonomy has 
not yet reached a stage where these methods 
can be applied to all new populations com- 
ing into the ken of the scientist, though surely 
all added experimental work, both in gene- 
tics and ecology, will aid the taxonomist in 
interpreting the morphological differences he 
finds. 
To evaluate a population and make it 
intelligible to other workers, a summary of 
definitions of the specific and subspecific cat- 
egories is in order. The following definitions 
merely indicate the difficulty of determining 
the genotype of a specimen or population 
from the phenotype with which the taxono- 
mist works. 
Biotypes are relatively slight morpholog- 
ical variations within a constant genotype 
which vary at random and which reflect no 
differences in the genetic constitution of the 
plant. Almost every individual could be 
classed as a biotype. 
Forms are groups of biotypes distinct from 
the other biotypes of similar genetic struc- 
ture by one or more very slight morpholog- 
ical characters which are either determined 
or probable responses to a peculiar environ- 
ment and may or may not indicate minor 
genetic differences. 
Varieties are groups of biotypes or forms 
morphologically distinct from the normal 
biotypic range of the population, these varia- 
tions being brought about by slight genetic 
differences and often subsequent isolation. 
Varieties in a population may interbreed on 
contact and show a degree of intergradation 
in morphological characters in some of the 
individuals. 
Species are populations of one or more va- 
rieties, forms, and biotypes which are clearly 
distinct morphologically from all other re- 
lated populations as a result of major genic 
differences. Interbreeding is usually restricted 
or impossible between related species though 
certainly radical genetic morphological dif- 
ferences may occur in isolated species with- 
out loss of the ability to interbreed. 
It is in no way intended to suggest that 
the above criteria are precise. In applying 
them to the populations of Hawaiian Carex 
it soon became apparent that both the bio- 
typic and formal variation were much greater 
than has normally been allowed for species 
of this genus. In the case of Carex tvahuensis, 
particularly, a tabulation technique was used 
giving all the possible visible or measurable 
characters by which species could be differen- 
tiated. Twenty of the most reliable charac- 
ters used to differentiate Carex species were 
recorded for each of the specimens examined. 
The tabulation showed clearly that, in what 
at first appeared to be several distinct species, 
the gradations between supposedly distinct 
characters were so complete as to make im- 
possible a delineation of more than one spe- 
cies. Only two minor characters in the peri- 
gynia (and these showing transitions with 
the typical) were found to be strong enough 
to be interpreted as of varietal worth. It is 
probable that even an able taxonomist con- 
fronted with a restricted number of speci- 
mens would have named several new species 
from among this group of specimens. 
Examination of the work of Mackenzie on 
the North American carices has made very 
clear the seriousness of dividing into species 
populations which are little more than bio- 
types. An effort has been made here to be 
somewhat conservative in the erection and 
retention of species. In defense of this ap- 
proach it may be said that the evidence 
strongly suggests extreme polymorphism in 
many of the groups. Though the species 
growing in the Hawaiian Islands may be dis- 
tinct, the world population has other species 
of very close affinities to almost every one 
of them. These affinities are indicated in the 
discussion following each description. Not 
only does the very size of the genus suggest 
an extremely unstable and rapidly ramifying 
