Re: Drosera, heterophylla, etc.

Jan Schlauer (Jan@pbc-ths1.pci.chemie.uni-tuebingen.de)
Wed, 17 Apr 1996 12:52:12 +0100

Dear Droseraceologists,

>> 3) Original Description of Drosera
>>
>> > Does anyone have access to the formal Generic description for
>> > Drosera?
>> Looking this up in the Index Kewensis, I found some interesting
>> information. The genus was originally described by Linne in his 1st
>> Edition of 'Systema Natura' which is dated 1735. That is interested
>> as that would mean that this description is to be neglected as it
>> predates 1. Mai 1753.

Yes, but the generic name and reference to previous description, together
with descriptions of the Linnaean species appear in Species Plantarum,
1.ed. (1.5.1753). Thus, the validating publication for _Drosera_ as a
generic name is Sp.Pl. and not later ones, nor Syst.Nat.. ...Just another
example for shortcomings of I.K..

>> There is indication of a second description by Bentham and Hooker
>> (fil) in their ' Genera Plantarum', Volume 1, page 662. According to
>> Taxonomic Literature (2nd. Edition) that is published on the 19.
>> October 1865. Whereby it remaines to be checked whether the taxon is to be
>> credited to Bentham or Hooker fil alone or to both.

The taxon is to be credited to Linnaeus alone (v.s.).

To return to the original question:
> Does anyone have access to the formal Generic description for
> Drosera?

What do you need the "formal Generic description" (I assume you meant the
protologue) for in the context of "irregular" flowers in _Drosera_? The
generic circumscription and content are essentially not dependent on the
protologue. Only the typus generis must always remain a part of the genus.
All other species are assigned to the genus due to taxonomic
considerations, nomenclatural ones (priority, protologue, typification) do
not play a great role. It is rather common that original generic
descriptions become inaccurate as further species are discovered.

BTW, In early systems, _Drosera_ was filed under Pentandra Pentagynia (i.e.
5 stamens and 5-parted ovary), obviously because the authors thought
_Drosera_ to be related to some "rosid" genera (in the light of more recent
data, a "caryophyllid" affinity seems much more likely for Droseraceae).
However, at least the type of the genus (_D.rotundifolia_) has a trimerous
(derived?) ovary. Some allegedly primitive species (_D.burmannii_ &
_D.sessilifolia_) do have a (primitive?) pentamerous ovary, however.

_Drosera heterophylla_ is another example (besides _D.pygmaea_) of a
species with usually non-pentamerous perianth. This species does normally
have more than five petals. In the whole genus variations of the numbers of
floral parts are rather frequent and normal. Occasional deviations from a
strict scheme give no reason to doubt the monophyletic nature of the genus
as a whole, however. IMHO, _Drosera_ is despite its size a highly natural
and very homogeneous genus with no need of generic segregation besides
_Drosophyllum_ (which in fact should be placed in a distinct family, apart
from _Aldrovanda_, _Dionaea_, and _Drosera_).

Kind regards
Jan