EGE A ES Oe MENU. CIEN WO RIT ee 
^ 
4 
E 
j 
7 
3 
3 
SPECIFIC RANK 7 
form overtaken their habitat within their geological history, or had 
they been forced by such changes to migrate into new and remote 
regions. Consequently the expected dying-out of less-adapted 
intermediates has not been as usual or complete in As¢er as in 
most genera even seemingly equally recent in origin. That com- 
mon criterion of species, the absence of intermediate forms, fails to 
be of avail in this and the other genera cited. 
Specific rank in Aster is indicated by continued development, 
while remaining in similar environment, of a body of characteris- 
tics which show a considerable degree of difference from the near- 
est kindred. Cases are rare in Aster where a single character 
alone distinguishes a species, however strong that character may 
Cases are numerous where a number of slight characters, on 
the other hand, mark, in their totality, a degree of difference cer- 
tainly sufficient to require recognition as a species. An example 
is A. vimineus as distinguished from A. lateriflorus; it is rightly 
separated and by all recent authors; but more on account of a 
fairly persistent combination of slight modifications than on ac- 
count of any one single character. 
Theoretically, each species of Aster is a family group, de- 
scended from ancestors not very remote, and in habit and also in 
less obvious characters distinguishable from the descendants of 
some other related collateral. 
We should limit the connotation of the idea of species to the 
existence of strong difference rather than to impress into the word 
species the explanation of the original difference. The word spe- 
cies does not itself tell us how the species has become individual- 
ized, whether by slow process of gradual modification responsive 
to a new kind of environment; or by gradual modification due to 
an innate variability acting in all directions at once, but of which 
variants only those best adapted to the environment have sur- 
vived; or by gradual modification due to an innate variability 
acting only in a certain direction which constitutes the line of pro- 
gressive change or evolution for that species; or by abrupt mod- 
ification, a sport or mutation, coming in full vigor, though un- 
heralded and unexplained; or, in the fifth place, by mixture of 
race as a fertile hybrid. It is quite conceivable that a species 
should originate in either of these ways, and however mise 
2M pd pue it deserves to be called a rcs 
