Use of the rank of forma

[Michael Chamberland]

I'm under the impression that the continued use of the rank of forma in
botany is generally discouraged.  Especially so for the "classic"
application of naming sporadic flower color mutants (usually white-flowered
individuals in typically red or purple-flowered plant populations, the
white flowers presumably the result of blockage of anthocyanin production).
 I can think of some arguments for not naming such plants as forma. 1) as
defined by a single character, white-flowered plants cropping up in any
population of the species may be referred to under this forma epithet, even
when the lack of anthocyanin expression may have been independently derived
or under different genetic control.  2) Anthocyanin-lacking forms have been
described in genera through much of the plant kingdom, and are to be
expected to be noticed among most flowers conspicuously colored with this
pigment.  3) The host of different forma epithets applied for these plants
are more confusing than referring them in the common vernacular as
"white-flowered forms".

My question is, should we continue to use the rank of forma for the
occasional sports which differ from the norm on the basis of one character
such as the loss of red pigmentation, loss of spination, loss of hairiness,
etc.?  Are there arguments for continuing to use this taxonomic rank for
such plants?  If not as forma, what would be the best nomenclature to use
for these plants, while avoiding confusing them with cultivar names?  I
have heard that attempts were made to remove the rank of forma from the
botanical code but these were unsuccessful.

Thanks,

Michael Chamberland
Assistant Curator
University of Arizona Herbarium (ARIZ)