dots absent
vegetation
working on
ape, usually
us florida
as such,
lis. season.
0,000 the
in of the
n in this
pes, rarely
s of snow.
0 feet, the
d (Cornus
' the same
will show
teristic of
mahogany
phing the
e different
> as is the
th a deep
in photo-
it is easily
ods.
(723)
Now how can this information be put in such shape as to be readily con-
verted into keys? The answer is that an experienced field botanist must com-
pile all the photographic characteristics and any pertinent extraneous infor-
Fig. 2. The very open white crowns of the sycamore or buttonwood (Platanus occidentalis L.)
are very evident in the winter, or leafless condition, much more evident than at other seasons
of the year. Note the fine, plush-like texture of the cat-tail marsh bordering the river.
mation into a table or chart or synoptic conspectus. From such a chart many
special keys can be compiled for many respective purposes. Perhaps the most
important use of such a chart is the ease with which several keys can be made
in order to verify or “Cross-check” determinations made by means of all the
other keys.
Perhaps the most important consideration in compiling such a chart is the
fact that any object to be recognizable must be different from (or in contrast
with) its surrounding or background in at least one visible characteristic repro-
ducible on at least one form of photography. According to Middleton the
human eye cannot see less than a contrast of 2%. But by various kinds of pho-
tography and instrumental aids, this contrast can be raised so as to be visible
to the eye, e.g. contrasts of less than 2% on black-and-white photography can
be increased by stereo effect; contrasts in color can be enormously increased
by the use of appropriately colored lights used with color transparencies. The
following is a list of visual characteristics which can be used for any type of
vegetation or individual tree in making a chart from which keys may be
derived.
