HOFFMANN: FLORA OF BERKSHIRE COUNTY. 175 
with the accompanying statement of habitat; thus, "Rich woods; 
common," implies that the species is infrequent or entirely absent 
except in rich woods. Moreover, the term "common" cannot be 
used with anything like mathematical precision. A species may be 
so designated if it occurs in fairly large numbers wherever the condi- 
tions are suitable, but ownng to its association wdth a number of other 
species struggling for space in the same en^^^onment the total number 
of plants in a given area may not be nearly so great as in the case of a 
species which crowds out all competitors. "Frequent" nieans that 
the species may be found without much search but that there are areas 
in many apparently suitable localities where it is absent. "Occa- 
sional " and " rare " explain themselves. When a plant is " occasional " 
or "rare," all the stations where it has been found have been given. 
The term "local" is used when a species is common at a few stations. 
Since the publication of the Manual a number of new species and 
varieties have been described, or the treatment of species or groups 
has been revised. Brief descriptions of these new species, varieties, or 
forms have been included in this list, generally copied from the original 
description, so that the list may supplement the Manual for the region 
which it covers. 
All varieties and forms have been given a separate paragraph for 
convenience in using the list, instead of combining subordinate varie- 
ties and forms in the same paragraph with the species. 
In a very few instances only, new combinations have been made in 
this list. A few combinations treated in the ]\Ianual as varieties have 
been reduced to forms, in accordance with the more recent treatment 
of these phenomena. The incised, or auricled forms of ferns, color 
phases of fruit or flower, which occur with the typical form and are 
not combined with any other character or any marked difference in 
range are treated as forms. A few color forms, most of which have 
been well known to collectors, but have not yet received a name, have 
been given names in this list. A list of all new forms and combina- 
tions is given in the Appendix. 
Artificial keys for the determination of species in large and difficult 
groups are an essential feature of the standard manuals of botany. It 
has seemed to the author unnecessary to furnish the present work 
with such keys, except where the number of species found in Berkshire 
County is much smaller than the number covered by the numuals. 
In such cases keys covering only the species known to occur in Berk- 
