Lace hedgehog cactus and its "orthostichies"

Note that the spines are arranged on 13 ridges, which match the number of petal-like tufts formed by the outer spines. In general, the number of rows stacked more vertically equals the sum of the number of spirals in both directions. Here: 13 = 5 + 8. Botanists call these more vertical rows "orthostichies."

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