classification

David Hershey dh321 at excite.com
Mon Apr 10 17:15:20 EST 2000


Your present some interesting questions. I'm no taxonomist but
taxonomist Cronquist's 1971 "Introductory Botany" text uses the terms
Psilotophyta, Lycopodiophyta, Equisetophyta, and Polypodiaphyta, the
last because Pteridophyta was traditionally applied to ferns and fern
allies, not just ferns. He says Charles Bessey coined most of those
terms in 1907. I would not be surprised if Psilophyta, Lycophyta,
Sphenophyta, and Pterophyta predate 1907. Dittmer's 1972 text "Modern
Plant Biology" says that Bessey's classification system was not widely
adopted because of its "unfortunate terminology" which may be a clue. 

One of the extinct genera, Sphenophyllales or Spenophyllum, was probably
the origin for Sphenophyta. Sphen- is Greek for wedge shaped.
Sphenophyta apparently predates Arthrophyta. Some botanists also object
to Arthrophyta because of its similarity to Anthophyta and the animal
phylum Arthropoda.

Microphyllophyta is much more descriptive than the Lyco- names but of
the 17 introductory college botany texts I own dating from 1955, only
one uses Microphyllophyta. The rest use Lycophyta, Lycopodophyta,
Lycopodiophtya or Lycopsida. It doesn't make much sense to name a plant
phylum after an animal species (lyco means wolf) which evolved hundreds
of millions after the first lycopods. However, we seem to be stuck with
it.  

Personally, I wouldn't rank scientific names of divisions/phyla too high
in importance in an introductory botany course. I'm not sure the common
names of the divisions/phyla are not more useful for students at that
level. Classification is only an approximation anyway, and there are
many classification schemes. It would be nice if the plant taxonomists
could agree on a single classification system and put the information on
a website as an international standard but that seems unlikely.

David Hershey


Janice M. Glime wrote:
> 
> Plant-edders,
>   I need your help in understanding the rationale for the names currently
> in textbooks for the divisions/phyla of plants.  While the International
> Code of Botanical Nomenclature does not require that the type concept be
> followed up to the phylum/division level, they do recommend it, and it
> makes more sense and is more stable.  However, introductory textbooks seem
> to be following a system for which I cannot find the rationale.  On the
> one hand, I do not mind using descriptive names like Coniferophyta or
> Anthophyta, but I do not understand the origin of the following:
> 
> Lycophyta
>   This is not the traditional descriptive name, which is Microphyllophyta,
> nor is it based on the type concept using Lycopodium as the root genus of
> the phylum, which would be Lycopodiophyta.  What is its origin and what is
> the rationale for using it?
> 
> Sphenophyta
>   Same problem.  The traditional descriptive name is Arthrophyta.  The
> type genus (without using fossils) is Equisetum, providing the phylum
> name Equisetophyta. What is the rationale for using Sphenophyta?
> 
> Pterophyta
>   Again, why not Polypodiophyta or Pteridophyta.
> 
>   Why Psilophyta instead of Psilotophyta (except for those putting in in
> Pterophyta).
> 
>   I know where the bryophyte phyla names came from, and have discussed
> Hepatophyta, Marchantiophyta, and Jungermanniophyta with liverwort
> systematists.  There seems to be a preference among the experts and recent
> publications for Marchantiophyta, based on Marchantia as the type genus,
> as well as being widely known.  However, textbooks are using Hepatophyta.
> 
>   Since the general biology and general botany books now seem to be
> switching to divisions (now that the International Code says Phylum is an
> allowable equivalent term) and switching to the names above, I find this
> to be a more difficult presentation to make to students because I cannot
> justify it.  I'd love to hear the thoughts of other teachers of plant
> science and to hear why these non-type non-descriptive names have emerged
> in current textbooks.
> 
> Thank you all,
> Janice
> ***********************************
>  Janice M. Glime, Professor
>  Department of Biological Sciences
>  Michigan Technological University
>  Houghton, MI 49931-1295
>  jmglime at mtu.edu
>  906-487-2546
>  FAX 906-487-3167
> ***********************************
> 
> ---




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