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Illustration of the five groups defined in the classification by five different species. Images are at the same scale. Vertical segments on each image are 1 mm long. (A) group 1, Conyza canadensis; (B) group 2, Nigella damascena; (C) group 3, Prunus persica; (D) group 4, Bryonia dioica; (E) group 5, Galium aparine.
