FEATURE
Let’s twist aga
last summe
Craig M
Current Address: ARC-AP, at the University of K
E-mail Address: m
“M y Dear Francis,” said Charles
Darwin, hesitantly, “your mother
said it’s time we had a little
torque.” “Come on, Father, don’t you
know I’ve been to school and already know
all that stuff,” snapped Francis (third son,
seventh Darwin child) irritably. “Ah, but do
you actually know how hygroscopic awns
of grasses work and what mechanism gives
them their torque – they must have some
ecological purpose.” “Right, Father, I’ll go
find out and tell you my results at lunch,”
offered Francis, helpfully.
So off went Sir Francis (M.B. FLS FRS FRSE)
to explore the nature of the hygroscopic
awn [he didn’t make it back to lunch], producing
one of the best pieces of investigative
botany I’ve read in a long time: ‘[On]
the Hygroscopic Mechanism by which certain
seeds are enabled to bury themselves
in the Ground’ (Darw
glass to carefully m
he examined how th
feather grass (Stipa p
wet, twisting again w
burying their seed, a
derlie this process. H
neer brother Sir Ho
Darwin son) to build h
groscope to measure
responded to his very
also moved towards th
awn was cooled or dip
Inspired by Francis a
(more about them la
out how the hygrosc
vourite productive a
Themeda triandra (F
whether long awns a
awns at transporting s
A
C
D
Figure 1: (A) Themeda triandra, (B) long and short awns, (C) the
in the helically coiled section of the awn, and (E) the daily movem
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