298 THE FORMATION 
Objection may be made that this analysis of formational structure has 
been carried too far, and that some of the structures recognized are mere 
interpretations, and not actual facts. Such a criticism will not come from 
one who has got beyond the superficial study of formations, for he will at 
once recognize that certain probable features of structure have not been con- 
sidered. On the other hand, the ecologist or the botanist who has not made 
a careful investigation from the standpoints of development and structure 
will naturally refrain from expressing an opinion, until he has obtained an 
acquaintance at first hand with the facts. Over-refinement is the usual pen- 
Fig. 79. Iridile (Iris missouriensis), a society of the aspen forma- 
tion. 
alty of intensive work. The unbiased investigator, however, will not be mis- 
led by the suddenness with which new concepts appear. It seems plausible 
that the structure of a formation, if not as definite, is at least nearly as com- 
plex as that of an individual plant. Few botanists will insist that the re- 
finement of tissues and tissue systems has been carried further than the 
differentiation of the plant warrants. Yet, if these had been defined within 
a period of a few years rather than slowly recognized during more than a 
century, they would have been called seriously in question. As a matter of 
fact, the consocies, under the term association, and the society, under various 
names, have been recognized by ecologists for several years. They are defi- 
