taxonomic language and theory

[p stevens]

Language and theory, ummm...  This gets tricky. (the message to which this is
replying to was a few days ago, but I have been having trouble with me
e-mail).

Clearly, one of the things that botanical latin (especially Stearn's) has
attempted to do is to stabilise the terms we use in plant description.  But
many of these terms are only peripherally connected with theory - for
instance, the various terms used for leaf shape, color, even indumentum.
These terms can be applied whether one is describing a fern frond or
angiosperm leaf.  When reading old descriptions, I never know how to
interpret lanceolate - is it what I would call elliptic, or some variant of
ovate?  It depends on the kind of spear-head one has in mind, I suppose.
Stabilisation at this level, it could be argued, is very worthwhile.  (It
could  also be argued that a precise description in terms of measurements
might utimately be more useful if we are to get character states from our
descriptions  Shape terms, etc., do not as terms refer to discontinuities in
the real world, just to a selected spectrum of variation.)

One area where there has been major activity in shaping terms to agree with
ideas of plant construction, etc., is in carpel type, inflorescences, and to
a certain extent fruits.  Little of this has filtered down to the level of
description, certainly at the species level, and one might question whether
we are the worse off for this - although inflorescence descriptions are often
difficult to follow, whatever the ideas that they are based on, and the terms
used in fruit description are a quagmire to trap the unwary (see Spjut's
recent work)).  However, terms like "ovary", "male" and "female" (when
applied to stamens and carpels) are very heavily theory-laden, and here I
often wonder what use they have in general systematic discussion (I am
writing as an angiosperm systematist).

At the same time, terms can constrain observation ("Oh, it is simply a
stipule"), and new ideas as to what might be going on in evolution,
development, etc., may help us to observe in a new way, or to see things we
had overlooked before.

P. F. Stevens.