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 to invest a bit of time
into learning the characters distinguishing the taxa within the group,
but the writer of the key/monograph also has a responsibility to write
the key so that a reasonably intelligent user can figure things out.
Nature does not operate for our convenience; sometimes a person doing an
ecological or a floristic survey will be forced to collect specimens that
are less than perfect. Writers of keys should realize this and enable the
users to figure out the specimen's identity anyway. They should, if at
all humanly possible,  avoid using obscure characters which they know are
difficult or impossible to observe, so long as alternatives are
available. I once saw a key separating two genera using the following
couplet:

Embryo curved
Embryo straight

The seeds of both taxa were about a millimeter in diameter. Another book
separated the exact same genera thus:

Inflorescence a spike
Infloresence a panicle

Which would you rather use? Embryo shape might be a more useful character
in determining the relationships of these genera to other groups, but
inflorescence shape is infinitely easier to determine.