DR KEITH WHEELER / SCIENCE PHOTO LIBRARY DR KEITH WHEELER / SCIENCE PHOTO LIBRARY
Cactus. Spines on a cactus. The arrangement of spines around the central point is according to the Fibonacci series, a number series in which each number is the sum of the two preceding it, for example 0, 1, 1, 2, 3, 5, 8, 13, 21 and so on.
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