18 VARIATION IN ASTER 
It will be readily seen that a species must often assume a com- 
plete disguise as it passes from one to another of these seven normal 
stages, and if it happen to enter into one of the accidental stages it 
may become still more unlike its proper self. Some species are 
especially prone to prolong certain stages or to accentuate them 
sharply. Specific distinctions are hardly to be found in the con- 
stant absence or the constant presence of any of the less usual 
stages, but rather in the relation which the plant bears to them 
when they are found, the ease with which they are induced, the 
shapes assumed when induced, and the speed with which they are 
thrown off. The character may remain latent in the species as a 
general thing, while circumstances have called it out in some indi- 
vidual. Species must usually be decided upon balance of charac- 
ters or total aggregate of features ; it is seldom that a single char- 
acter in Aster will prove absolutely specific. 
Sylvanism and other sources of change. — Many other modes 
of variation are occasional. Some temporary stimulation may 
have suddenly increased the internode lengths, so separating 
the leaves sufficiently to produce a new effect. Sudden influx of 
light or the cutting away of a neighboring tree may have induced 
unwonted size and number of radicals or may have changed the 
divergence of peduncles or pedicels. Unwonted shade may have 
reduced the thickness, roughness or pubescence of leaf. Such re- 
sults of sylvanism may be temporary, and may even affect but part 
of the leaves or the inflorescence, or may not appear in the same 
plant the year following ; yet they influence the aspect greatly, and 
are among the chief factors in the uncertainty often felt regarding 
aster species. 
COMPARATIVE VARIABILITY OF CHARACTERS 
AMONG ASTER SPECIES 
VARIATION OF SEEDLINGS 
In the lack of a garden, and having need to conduct my 
observations in the time which could be spared from routine 
work of instruction within the city, I have had little opportunity 
to investigate the variability of aster seedlings as indicated by suc- 
cessive sowings. Long-continued observations of this kind are 
