1913] Book Review 221 
“many species, perhaps all, are composed of a greater or lesser number 
of races, differing from each other too little to cause them to be re- 
garded as species, notwithstanding the fact that they may breed true 
from seed to such slight or trivial differentiations... In the present 
edition. ..the view is taken that the races composing many species 
are often too numerous and too slightly characterized to be described 
so as to be recognized; many of them have been described as species 
and many more as varieties, and varieties of different degrees of differ- 
entiation have been suggested. We here regard species alone as 
entitled to distinct botanical appellation..." In accord with this 
doctrine the names and descriptions of varieties have as a rule 
been omitted from the second edition. 
It is just as true today as it was a generation ago that there is no 
unfailing or even generally applicable criterion as to what constitutes 
a species. Asa Gray said that “species...are not facts or things, 
but judgments, and, of course, fallible judgments; how fallible the 
working naturalist knows and feels more than any one else" (Letters, 
vol. ii, p. 657). Darwin said that “few well-marked and well-known 
varieties can be named which have not been ranked as species by at 
least some competent judges" (Origin of Species, 6th ed., p. 37). 
Certainly any author who assumes to write about species only, to 
the exclusion of varieties, providing, of course, that he does not con- 
sider every distinguishable form as a “species,” places a higher evalu- 
ation on his own judgment than anyone else is likely to do. And when 
he remands to synonymy species which he arbitrarily decides to con- 
sider as varieties (or * races") and almost in the same breath announces 
that the aim of his work “is to illustrate and describe every species... 
recognized as distinct by botanists" (v. introduction, p. v; italics the 
reviewer's) we may well be pardoned some display of astonishment! 
What will they say who were formerly wont to protest long and vigor- 
ously against botanical dictatorship? For now Dr. Britton not only 
decrees what species are species but even what botanists are botanists! 
Dr. Britton's failure to attempt a rational treatment of varieties 
and critical species unfortunately involves a neglect of the very prob- 
lems which bring taxonomy most vitally into touch with other kinds 
of botanical investigation. From many standpoints the forms which 
are generally treated as critical species and as varieties are of greater 
interest than the more conspicuous but often not sharply defined 
groups which by common tradition have long been classed as species. 
Even if the varieties can not be sharply distinguished from the 
species, and if the critical species rest upon technical characters, they 
should by no means be omitted from any descriptive flora which is 
designed to be of general interest and utility. A few examples will 
bear out the truth of this. In the new Illustrated Flora Scirpus 
georgianus is placed in the synonymy of S. atrovirens; of Scirpus atro- 
cinctus we are told little except that it “may be specifically distinet” 
from S. cyperinus; it is said of Scirpus Longii that it “appears to be 
