136 FLORIDA GEOLOGICAL SURVEY-SEVENTH ANNUAL REPORT. 
world and absent from another where conditions are favorable for 
it, simply because it has not had time or opportunity to reach the 
latter place since the conditions became favorable. A much more 
important factor in limitedareas is fire. Two areas of the same kind 
of soil, one protected from fire by being surrounded by water or 
some other barrier and the other not, may have very different vege¬ 
tation, as is exhibited in many places in the Ocala area, and will be 
discussed below. 
Most previous studies of vegetation have included lists of plants 
arranged in taxonomic or in alphabetical order (which is conven¬ 
ient for reference but has little significance), or worse still, merely 
in the order in which they happened to be observed or thought of, 
with little or no indication of relative abundance. But abundance 
is all-important, for naturally it is the most abundant species that 
give the vegetation its character. It would be possible for example 
for two forest areas to contain exactly the same species of trees, 
but in very (different proportions, so as to give the forests quite differ¬ 
ent aspects and indicate very different soils. 
In the plant lists below the species are first divided into trees, 
small trees or large shrubs, vines, shrubs and herbs, except where 
one or more of these classes is absent or where two of them are 
combined for some special reason; and the species in each class are 
arranged as nearly as possible in order of abundance.* * The rarer 
species of flowering plants and ferns, and all the mosses, lichens, 
fungi, etc., are omitted, partly because of some uncertainty about 
their correct identification, and partly because the importance of a 
species in vegetation studies is believed to be directly proportional to 
its size and abundance. The rare species are indeed interesting to 
mere collectors, but their value as indicators of environmental con¬ 
ditions is negligible. As the field work on which these lists is based 
has been done mostly in spring and summer, it is quite likely that 
some herbs that bloom only in the fall have been overlooked; but 
this difficulty does not apply to the trees and shrubs. 
O11 account of the limited amount of field work that has been 
done on some of these vegetation types, and for other reasons which 
will appear, the figures representing the relative abundance of each 
species are not published, though some conclusions drawn from 
them, which are not likely to be affected much by more thorough 
work which may be done hereafter, are given in their proper places. 
*For a discussion of methods of quantitative analysis of vegetation see 6th 
Annual Report, pp. 177-180. 
