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On Sun, 28 Oct 2001, brian whatcott wrote:
> I read about Chladni's figures (1787) when I was a kid.
> A glass square is supported from the center on a stand,
> and lycopodium powder - whatever that is - is sprinkled
> over it,
Lycopodium powder is actually the spores (vegetative propagules) of
various species of Lycopodium, "clubmosses" vaguely related to ferns.
especially the spores of Lycopodium clavatum, aka "running
groundpine". A pressed plant is shown at:
<http://www.portableherbarium.com/Lycopodium-clavatum.jpg> (the spores
are in the golden structures to the upper right of this herbarium
specimen -- they're the fine dust you can sort of see surrounding
these "cones" (strobili).)
The spores themselves are quite small, about 25-28um and look like
this (SEM toward the bottom of the page) :
<http://www.botany.hawaii.edu/faculty/webb/BOT311/LycoRepro/LycoRepro1.htm>
They're also the source of the Victorian's "flash powder" and one used
for theatrical effects -- they have a high oil concentration, so they
do a very nice "grain dust explosion" -- they're also quite liable to
provoke asthma, which is probably a good reason not to use them
regularly in a science museum setting where dust can blow.
They're still collected now, and used by palynologists (pollen
specialists) to help determine pollen concentrations in a sample.
http://www.ualberta.ca/~abeaudoi/cap/supply.htm
Kay Lancaster kay@fern.com (stray botanist)