An Identification key is a Quick and Easy means of identifying an unknown object.

At least, that is the goal. Writing good keys is not easy. It requires that you really know the taxa you wish to key out. Writing keys is also an excellent test of your knowledge of a group, and forcing yourself to write keys will help you learn the characteristics of whatever group you are studying. In this class you will be asked to write keys as a test of your knowledge - and as a learning device.

We shall spend most of our time preparing indented, dichotomous keys. These are the kind that you will find in Shaw's Vascular Plants of Northern Utah and the Intermountain Flora. I like them because they make it easy to see which species or families are alike, and alike in which key characters. They do, however, take a lot of space. The alternative style for written keys is found in Welsh et al. (1993), A Utah Flora. In this non-indented style, pairs of opposite leads are always together. This makes it easy to compare what each lead asks for but harder to see which species are alike and how they are alike. The major advantage of non-indented keys is that they do not require as much paper.

The second kind of key that we shall write, but as a class exercise, is an interactive, multimedia, computer based key. These are, in some respects, demanding to write, but they offer several advantages that a paper and pencil key cannot offer.

Good Keys
Before starting to write keys, it is worth thinking about what makes a key "good".

Reliable characters
Visible characters
Clearly understood character states

The next consideration is style, how should the leads be constructed?

Parallelism, parallelism, parallelism
Name the structure first, then its condition
Use characters that can be seen under reasonable conditions (naked eye, hand lens, dissecting microscope are descending levels of 'reasonable conditions')
Use characters that provide a clear contrast, if at all possible
Be explicit: "Styles shorter than the ovary” or “Styles less than 2 mm”, not “Styles short”
Avoid "Not as above" and "Leaves variable".
If feasible, use both a vegetative and reproductive character in each lead

For class purposes, work first on providing a key that will work, then on refinements. Write your key for the usual condition in a family. You may key a family out twice so that the exceptions are taken care of. You can also use this strategy for variable families, but try to avoid it.