Musa corms

Mon, 04 Jun 2012 14:35:50 PDT

Thanks for your reply.

For us, and the other two growers who care about such things, a corm can be
hypothesized to be a modified rhizome by reduction through evolution.

However, I would ask what is the usefulness in saying to someone about his
"Crocus bulbs": "Well, they are called corms but really it is just a fancy
type of rhizome". What constructive purposed is served by this approach?
Where would you draw the lines, if any, between the few most basic terms
for geophyte rootstocks? It is not as if corms (sensu stricto) and rhizomes
are scattered randomly through the plant kingdom and their presence is not
predictive. Gingers are generally rhizomatous (no corms!)  as we have
learned, many irid genera and Tecophilaeaceae are wholly cormous, etc. If
the rootstocks of a few taxa hold on to older corms or present a
'vestigial' rhizome we can still call them corms. Some cormous groups may
have a few rhizomatous taxa and vice-versa. Biological terminology is
supposed to be flexible in this way, even when applied definitions are
fuzzy.To advocate against practical morphological distinctions and
classifications, whether putatively homologous or analagous, runs counter
to the function of the descriptive natural sciences.

Other structures present real problems. "True bulb" examples like Lilium,
Calochortus, Tulipa, Massonia and Oxalis are all very different in a
variety of ways and it appears their bulbs are not altogether homologous
structures. If they are not homologous but only analagous then would you
have new terms coined for the different types of "bulbs"?  I think it is
fair to say that in botanical terminology both* differences in kind and in
degree* may be in play for the same term. But merging basic concepts
together, i.e., erasing boundaries between rootstock types via evolutionary
hypotheses of homology accomplishes little that is applicable outside of
theoretical (phylogenetic) considerations. Interesting, yes, but not
constructive or practical. Many plants will not fit neatly into any
roostock category and that is ok.

I'm not sure what you mean when you say that "...the only fact is that it
is what it is regardless of what we call it".
You indicate that you wonder if it is worth all the fuss to labor at length
over such subjects. The query answers itself I think and if others agree
then the effort is worthwhile.


On 4 June 2012 12:42, Jim McKenney <> wrote:

> Dylan, here's the way I look at this discussion.
> There are people who believe that the answer to these questions is merely
> a matter of definition: once the definition of corm is in place, and the
> definition of rhizome is in place, then the difference between the two is a
> difference in kind.
> On the other hand, there are people (this is my camp) who believe that
>  what we call typical corms, as in most crocuses,  evolved from rhizomes
> (remembering that some crocuses produce rhizomes, too),. To this camp,  the
> corm is simply a much compressed rhizome. Or rather, to interject the
> important distinction you made when we discussed this in the past, the corm
> is a much compressed modular rhizome. For people in this camp, the
> difference between a corm and a rhizome is a difference of degree.
> Those who believe a difference in kind is involved will no doubt insist on
> sharp distinctions and, since such distinctions are not characteristic of
> the way things happen in nature, will no doubt find themselves involved in
> this discussion for a long time.
> Those who believe a difference in degree is involved are probably content
> to recognize that while  some people might consider a given structure a
> corm and other people  might consider the same structure a rhizome, the
> only fact is that it is what it is regardless of what we call it.
> Dylan, when I read what you wrote "Would you agree that it is important
> todiscern structures morphologically as well? I think it is important to
> recognize that there is a useful degree of precision-- limited though it
> may be-- in defining terms for geophyte rootstocks."
> I had to wonder if what you meant when you said "discern structures
> morphologically" was that things which look alike (structures discerned
> morphologically). even when they are analogous rather than homologous
> structures, deserve the same useful degree of precision of definition
> routinely given to homologous structures. If that is what you meant, I
> think I would disagree for at least two reasons. For one, if the structures
> in question are analogous rather than homologous, then the distinctions
> between them are on the level of importance of the level of the
> distinctions to be made between insect wings and bird wings. Yes, it is
> important to learn the basic distinction (your limited useful degree of
> precision), but is it really worth a lot of discussion? The other reason is
> this: a system based on analogous distinctions will always be in tension
> with one based on homologous distinctions; and since most people will
> recognize the homologous distinctions to
>  be more natural than the analogous distinctions, the system of analogous
> distinctions will suffer a constant attrition as more and more people come
> to understand the homologous distinctions.
> I can't believe I wrote that on such a beautiful spring day! I need some
> sunshine.
> Jim McKenney
> _______________________________________________
> pbs mailing list


"*Reason is itself a matter of faith. It is an act of faith to assert that
our thoughts have any relation to reality at all.*"

~ Gilbert K. Chesterton

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