and Winter Keys
As a further help in identification of these fifty trees in both summer and winter condition, keys have been created.
A key is a scheme for easily and quickly identifying any unknown object under observation. It is based usually on the most striking similarities and differences shown by the various parts of the object. In trees, the leaves (plate 1) have been selected for the summer key and the twigs and buds (plate 2) for the winter key because they present the most easily available parts of the tree for showing differences and similarities.
|Two alternative characteristics are presented.
These are the only choices possible. The two opposing characteristics are preceded
in the key by the same number (1 and 1 or 2 and 2) and are set at the same distance from
the left-hand margin of the page (when permitted on the screen). Often, 1 and 1 are
subdivided further into other groups on the basis of other differences; in every case,
however, the characteristics are opposed. If you find the desired characteristic in
the first group (1), there is no need to look in the second group, and study need be
confined to the subdivisions of the first group only.
The most important distinguishing characteristics
of trees in the summertime are the form, arrangement, shape, and margin of the leaves.
In the wintertime, the size, color, and arrangement of the twigs are important, and
the position (terminal or not), size, shape, and color of the bud. Be sure you
thoroughly understand the illustrations in plates 1 & 2 and learn the distinctions before you attempt to use the key or go
into the field.