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Mosses and more....
Nick Wise posted a lisiting of Fontinalis and Vesicularia species which are
reported to be found in the United States (thanks Nick). It is reported to
be a listing recognized by the USDA (U.S. Dept. of Agriculture).
Maybe they have several lists.....
I have checked with the main USDA Plants Database
[http://www.itis.usda.gov/] and the listings they have there don't quite
agree with what Nick posted. In particular, they only list one species of
Vesicularia in the U.S.
One other source I have consulted contained a caution regarding the validity
of lisiting for Vesicularia amphibola, stating that it is an exotic and
"probably collected only in nurseries and greenhouses" (i.e. your aren't
likely to run into it in a local stream). ["Preliminary Annotated Listing of
Moss Species Reported to Occur Within California", by Stephen P. Rae (found
on the web @ http://www.musci.com/musci/CA-list/SPP-LIST.html)]
Lists or species are great, but they aren't really of much help at this
point in time. I have also been trying to understand the higher taxon
organization of different plants to see where different species fall.
In looking at the various databases and checklists which are available
online it would appear that there is very little agreement amongst the
"experts" as to how the Plant Kingdom should be organized and presented. Its
quite possible I suppose that recent work with DNA analysis is causing some
rethinking of how particular plants relate to one another.
The USDA Plants Database provides information regarding the base "lists"
that went into the making of the data sets. The databases of the Royal
Botanical Gardens at Kew seem to use a different set of lists, or at least
organize them in different ways. As stated in one place - "Higher-level
classification of the mosses is still not fully settled, and there is still
considerable difference of opinion on the names of the major groups".
The USDA Plants Database also forms the basis for the ITIS Database, another
"listing" which attempts to present taxonomic placement of living plants.
Canada has its own version of ITIS (ITIS*ca) and it includes many groups of
algae in within the Kingdom Plantae while most other authorities still place
them in the Kingdom Protista. The U.S. version of ITIS doesn't do this, nor
does the USDA Plants Database. Maybe its just a "Canadian thing, 'eh?"
The same sort of confusion also occurs within the plants called "Ferns". In
a recent article in PAM, Karen Randall lists Horsetails (Equisetum) and
Quillworts (Isoetes) as being within the basic phylum (division)
Pteridophyta. I have seen classification "schemes" which follow this
thinking. But in the USDA Database, Equisetum is placed in a division of its
own (Equisetophyta) and the Isoetes are placed in the division
Lycopodiophyta (which also contains the Club Mosses, Lycopodium). The plants
we think of as "ferns" are listed in another division - Pteridophyta.
Within that division, I have also seen differences in the placement of
Azolla - some authors show it as being grouped with Salvinia while others
give it equal status as a "family" separate from Salvinia.
Moving to the seed plants, I see major differences of opinion and
organization in the different databases. The USDA Database follows the basic
organization scheme devised by Cronquist in 1981. I have seen other
databases which follow other author's organization schemes, and seen some
authors give the same sort of short shift to Cronquist's work that I have
seen given to that of Rataj.
I have been advised privately by one person on the list who probably knows
far more about this stuff than I do that this is a field which laymen should
steer clear of because unless you are an expert it will never make sense.
Talk about waving a red flag in front of a bull.
I don't pretend to know anything about this and my interest in it is purely
personal curiosity - but is there ANY generally accepted classification
scheme which _most_ authorities agree upon? Or are they all as confused as I
am now?
Tom Barr.....if you read this....what are they teaching you in school? Do
any of your professors know anything about plant taxonomy?
James Purchase
Scratching my head in Toronto