By topic: 257
Observer, 21 October 1923, p. 19 col. C
In book: 132d
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Tendrils of briony (AW)

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THE CREEPER AS A COMPASS.


Sir,—The tendril of an English briony, which it sends out to anchor itself to some support, is straight at first. But with growth it develops a spiral. To form a simple spiral, one end must be free to revolve. But in this case both ends are fixed. And so, midway, a kink is formed which is free to revolve. On one side of the kink the spiral is right-handed, on the other side of the kink the spiral is left-handed.

The double spiral gives an elastic anchor cord, and can be pulled out to a straight line without snapping, which would be inevitable with a single spiral To put it another way, the plant throws out a spiral tendril which is right-handed part of the length and then changes to a left-handed spiral. It is difficult to see how the sun can decide this.
Alfred Watkins.
Hereford  

 

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