Bad taxonomic keys -some su

[Joseph Laferriere]

On Fri, 29 Sep 1995, Warren Lamboy wrote:
>
>  A user of a taxonomic key must
> invest some time in learning the key features of the taxa of interest.  Even
> if one does this, however, there are still problems with keys of the above
> sort.  First, one may not have all of the requisite characters available in a
> particular specimen (this is hardly the fault of the maker of the key,
> however!).

Sure it is! Granted, the user of the key has some responsibility to learn
the characters involved, but the writer has the responsibility to make
the user's task possible. Writers should know which characters are easy
to determine, which are difficult to determine, and which ones the user
is unlikely to have available at all. Keys which require, for example, both
floral and fruiting characters for species which never have flowers and
fruits on the same specimen at the same time are totally useless. Easy
characters should be used if at all humanly possible. For example, I once
saw a key separating two plant genera using the following couplet:

Embryo straight
Embryo curved

The seeds of both taxa are less than 1 mm long. Another key to the exact
same genera read:

Infloresence a spike
Infloresence a panicle

Which would you rather use? Embryo shape may be very useful
taxonomically, but is useless as a field charaacter, of even a herbarium
character without a great deal of effort.