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<title>Dendrological Dexterity - Comfortably Numbered</title>
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<a href="/"><span class="left-word">Comfortably</span> <span class="right-word">Numbered</span></a>
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<article id="postcontent" class="centered">
<section>
<h1>Dendrological Dexterity</h1>
<center><em><p>Thoughts on the chirality of the wood grain in eucalyptus trees</p>
</em></center>
<h4>Wednesday, December 25, 2019 · 4 min read</h4>
<p>It’s Christmastime, shall we talk about trees?</p>
<p>I was reading about Knuth’s <a href="https://www-cs-faculty.stanford.edu/~knuth/fant.html">Fantasia
Apocalypta</a>, and his
description of the “style” he wrote it in contains the wonderfully Knuthian
line “And of course a musical work on the Apocalypse should also contain
calypso.” Naturally I had to look up whether or not this was a linguistic
coincidence, and — in an odd turn of events, since these things usually tend
to work out — it turns out that <em>apocalypse</em> and <em>calypso</em> are <em>not</em>
etymologically related. <em>Apocalypse</em> comes from the Greek root <em>kaluptein,</em>
“to cover,” and so the <em>apocalypse</em> is the “uncovering” or “revelation” (the
root <em>kel</em> is related to <em>hell</em>). The word <em>calypso</em> is of unknown origin, but
from the West Indies (this is distinct from <em>Calypso,</em> the Greek mythological
nymph, whose name is indeed related to “covered,” or “concealing”).</p>
<p>I shared this with a good friend of mine and she immediately pointed out that
we should check out the word <em>eucalyptus</em>. She was right: <em>eucalyptus</em> means
“well-covered,” referring (not ironically to the bark as I originally thought
but rather) to the calyx, which <a href="http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/artoct07/bj-eucalyptus.html">forms a lid over flowers when in
bud</a>.</p>
<p>That got me thinking about eucalyptuses…</p>
<hr>
<p>Lately I’ve spent a lot of time around the eucalyptuses in <a href="https://trees.stanford.edu/ENCYC/EUCnotes.htm">Toyon and Arboretum
Groves</a> at Stanford and I’ve
noticed that the peeling bark of what I’m 80% sure is the <a href="https://trees.stanford.edu/ENCYC/EUCglo.htm"><em>Eucalyptus
globulus</em></a> (Tasmanian Blue Gum)
seems to climb up the tree in a whirling, helical pattern. I didn’t have the
presence of mind to take a picture at the time but here’s a picture <a href="https://commons.wikimedia.org/wiki/Eucalyptus_globulus#/media/File:Starr_031002-0027_Eucalyptus_globulus.jpg">from
Wikimedia
Commons</a>
taken in Maui.</p>
<p><img src="static/eucalyptus-grove.jpg" alt="lots of whooshing eucalyptuses"></p>
<p>Really it’s just beautiful to me, the whorl reaching aspirationally towards the
sky. I’m reminded of Correggio’s <em>Ganymede Abducted by the Eagle</em>, the way the
dog and the tree stump look up together, moving, turning even while frozen in
the painting.</p>
<p><img src="static/correggio.jpg" alt="correggio's abduction of ganymede"></p>
<p>This much would be believable, just another quirk of nature. But here’s the
truly odd thing: most of the trees seem to grow according to a thumbs-up
right-hand rule; if you were to try and screw them into the ground you would
turn them righty-tighty. <em>So eucalyptuses have some kind of chirality?</em> I
rubbed my eyes, I thought I was dreaming.</p>
<p>But indeed, some hours of study later, I learned that the “spiral grain” is a
real thing in the study of wood formation.</p>
<hr>
<p>In the Real World of economics spiral grain is considered a defect because it
reduces the structural quality of wood. But let us set that aside for a moment
and marvel at the phenomenon itself. I turn to Dr. John Maddern Harris’
wonderfully comprehensive 1989 text <em>Spiral Grain and Wave Phenomena in Wood
Formation</em> (thanks Chandler for finding me a copy!) for details. Harris, citing
confusion about the convention in prior work, carefully defines LH (left-handed
“sinistral”) and RH (right-handed “dextral”) spirals (I wonder if he was aware
of the right-hand-rule convention from E&M, which would simplify matters here).
Perhaps more entertainingly Harris introduces the German words as well:</p>
<blockquote>
<p>Numerous other expressions have been used to describe spiral direction,
reflecting no doubt the notorious difficulty of so doing without waving of
arms and twisting of wrists. In the German literature the terms “sonnig” and
“wider- sonnig” are frequently encountered. Their meaning is “with the sun”
and “against the sun”, and hence (in the Northern Hemisphere!) they relate to
LH and RH spiral grain respectively.</p>
</blockquote>
<p>Here’s a picture of a eucalyptus from Harris’ book.</p>
<p><img src="static/eucalyptus-spiral.png" alt="spiral-grained eucalyptus"></p>
<p>Certain species do indeed show predilections for certain handednesses.
Furthermore, certain species <em>change</em> handedness over the course of their
lives. In Harald Säll 2002 doctoral thesis <a href="https://www.diva-portal.org/smash/get/diva2:206846/FULLTEXT01.pdf">Spiral Grain in Norway
Spruce</a> I
learned the remarkable fact that the Norway Spruce begins life as a left-handed
spiral grain, but over the decades transitions to a right-handed spiral grain.
The drawing below is from his thesis:</p>
<p><img src="static/spruce-spiral.png" alt="spiral grain reversal in spruce trees"></p>
<p><a href="https://www.conifers.org/topics/spiral_grain.php">We don’t fully understand why trees
spiral</a>, much less how they
pick a direction. The most fanciful explanation I’ve come across — the one I
would like to believe — is that there is some kind of Coriolis effect at
work. But I will admit that both handednesses have been observed in both
hemispheres, which weakens that theory.</p>
<p>At the moment I’m on a quest to find a (translated, ideally) copy of Meyer’s
1949 article <em>Sprachliche und literarische Bemerkungen zum Problem “Drehwuchs”</em>
published in <em>Mitt Schweiz Centralanst Forst Veruschswes</em> (26:331-347) to learn
more about the linguistic history of chirality in relation to spiral grains.
Until then…</p>
<p><strong>Open question:</strong> What’s going on here, why are eucalyptuses right-handed?</p>
<p><strong>Further reading:</strong> Noah Rosenberg’s
<a href="https://xtrees.sites.stanford.edu/tree-gallery">Xtrees</a> site about Stanford
trees — I found this while reading about eucalyptuses!</p>
<p>Edited to add (2/19/2020):</p>
<blockquote>
<p>“DNA normally forms a right-handed spiral (although a rare left-handed
variant can occur). In other words, it twists like a conventional screw.
That, though, has not stopped it being reproduced wrongly in hundreds of
places. Dr. Tom Schneider has a website where he has collected hundreds of
examples of incorrectly drawn ‘left-handed DNA’, most being found in
scientific journals. Many are in advertisements, so we may perhaps charitably
suggest the final copy was never seen by a scientist, but that doesn’t quite
explain them all. Certainly not the editorial comment in Nature, the place
where DNA’s structure was first described, which in 2000 mentioned the clues
that ‘led Watson and Crick to deduce the left-handed double helical structure
of DNA.’ Watson, in fact, has been particularly badly served, his 1978
textbook, Molecular Biology of the Gene, having six different illustrations
with left-handed DNA, and in 1990 the American journal Science quoting Watson
as saying, ‘I have to read SCIENCE every week,’ this being illustrated with
left-handed DNA. Perhaps worst of all, a 1998 reprint of Watson’s The Double
Helix was illustrated on the front and back with left-handed DNA. Perhaps it
is not a coincidence that Watson is left-handed.”</p>
<p>— Chris McManus, in Right Hand, Left Hand: The Origins of Asymmetry in
Brains, Bodies, Atoms and Cultures. 2002.</p>
</blockquote>
</section>
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