Use of the rank of forma

[Jacques Melot]

 Le 1/10/00, à 17:53 -0400, nous recevions de John McNeill :

>Like Richard Jensen, I have never felt that there was a biological
>situation for which the rank of forma was useful; "white-flowered
>variant" or "glabrous glumed plants" are more informative than
>"forma alba" or "forma glabra" (in that the white or glabrous organ
>is indicated).  I cannot remember, however, any proposal to remove
>the rank from coverage by the International Code of Botanical
>Nomenclature.  Personally, I think its main period of use has passed
>and was for single-character (and often single-gene) distinguished
>individuals that "caught the eye", and that had its heyday before
>the advent of the International Code for the Nomenclature of
>Cultivated Plants.  Now, if the human eye is caught in a way that
>makes cultivation of the variant desirable, the cultivar category
>under the ICNCP is clearly the appropriate one to use Ø particularly
>as it let's one distinguish all sorts. say, of different white
>heathers, with different foliage features, flower size etc. Ø
>whereas all might be accommodated as _Calluna vulgaris_ f. _alba_
>
>But the ICBN, like the ICZN, does not seek to influence taxonomic
>practice, merely to provide the mechanism for unambiguous naming of
>taxonomically recognized groups.  If, some day, use of "forma" has
>totally atrophied, it may be removed from the Code, but whether
>included or excluded, the decision on usage is a taxonomic not a
>nomenclatural one.  [Of course, the zoological Code does not
>regulate any rank below subspecies Ø except indirectly to declare
>that early varieties are to be treated as subspecies].
>
>John McNeill
>
>---------------------------------------------------------------------
>--------------------------
>John McNeill, Director Emeritus, Royal Ontario Museum;
>    Honorary Associate, Royal Botanic Garden, Edinburgh.
>Mailing address:
>Royal Botanic Garden, Edinburgh, EH3 5LR, Scotland, U.K.
>Telephone:    +44-131-248-2862;  fax: +44-131-248-2901
>Home office:  +44-162-088-0651;  fax: +44-162-088-0342
>e-mail:  jmcneill at rbge.org.uk or johnm at rom.on.ca
>---------------------------------------------------------------------
>---------------------



    Le rang de forme est encore tres utilise en mycologie (les
nomenclaturistes non mycologues ont trop tendance a oublier ce
domaine de l'histoire naturelle!).

    De plus, la suppression du rang de forme serait peu compatible -
dans l'esprit et a la lettre - avec l'art. 4.3:

4.3. Further ranks may also be intercalated or added, provided that
confusion or error is not thereby introduced.

    En realite, si le rang de forme (ou un autre) n'est plus utilise,
il n'est pas necessaire a priori de le supprimer du Code. De plus, il
est necessaire que le Code indique comment traiter les formes deja
publiees.

    Jacques Melot (Reykjavik, Islande)





> >>> Michael Chamberland <chamb at U.ARIZONA.EDU> 09/29/00 05:40pm >>>
>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)