What is a bulb?

Hannon othonna@gmail.com
Mon, 07 May 2012 18:24:52 PDT
Dear Andrew,

My understanding has always been that the term "geophyte" directly implies
that the plant in question has some connection to the earth (*soil*) by way
of perennating buds that see it through an unfavorable (dry or cold)
season. If we say that these buds must be subterranean, which they
typically are, in a strict sense then we lose plants that obviously belong
with our other friends, such as Worsleya, Bowiea, etc. Whether epiphytes
can be geophytes (!) is an interesting area to explore and it would not be
so intimidating a subject if the orchids were excluded.

In the case of the pseudobulbous orchids the storage organ strategy is not
typically dependent on any earthen refugium and so to call them geophytes
is in error I think. This contrasts with terrestrial orchids with
'tuberoids' of course, which fit the definition of a geophyte very well. As
Nhu mentions, the radical cultural differences between terrestrial bulbs
and epiphytic orchids are also significant.  If there is agreement in this
area then you are right that "pseudobulb" should be deleted from the key.
The term pseudobulb is never applied to any plants except certain orchids
as far as I know-- if it is applied to Crinum &c this should be explained
and documented in the key.

Beyond these points I think Nhu is absolutely correct that it is best to
avoid including more than a sampling orchids in light of the massive
support they receive already from many scientific, hobbyist and commercial
groups. For growers who may be still forming their ideas of what a "bulb"
is, which task is a priority for the PBS it seems to me, it is instructive
to see tuberous terrestrial orchids on the wiki and I think this helps to
show that the concept of a "bulb" (geophyte) transcends many plant
families. Terrestrial orchids with pseudobulbs like Pleione are problematic
in this regard but what else is new?


On 7 May 2012 17:44, AW <awilson@avonia.com> wrote:

> Dear Nhu Nguyen,
> I was totally surprised by your most recent posting. It seemed to be in
> flat
> contradiction with the key in 'What is a Bulb', inserted to define what was
> acceptable to PBS as a bulb. I thought that was meant to provide the
> defining word here. Question 2 of the key says: "2. Is the plant generally
> recognized to grow from some sort of thickened storage organ (a bulb,
> tuber,
> corm, thickened rhizome, thickened root, or fleshy pseudobulb)? In other
> words, would scientists call it a geophyte? If the answer is yes, we
> include
> it. If no, go to question 3".
> Thus, the presence of a thickened storage organ is a criterion for
> acceptance, which means that orchids possessing fleshy pseudobulbs are
> accepted. If you have subsquently decided not to include them you had
> better
> correct the key.
> I wrote a message here yesterday showing an orchid with a massive set of
> fleshy pseudobulbs. It would certainly be far closer to what we think of as
> a clump of bulbs than so many other genera considered here. Indeed the
> pseudo bulbs do look comparable to your example of 'Crinum and Ismene'.
> Living atop granite outcrops the orchid cited uses its massive pseudobulb
> system to store water during the long, cool dry season. If the preference
> of
> PBS to eliminate such plants, so be it, but you then really do need to
> reformulate 'what is a bulb'.
> Andrew
> San Diego
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> http://pacificbulbsociety.org/pbswiki/


"*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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