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Successive growth units may be delimited (arrows) only by more or less marked changes in leaf size (Virola michelii, A; Virola surinamensis, B; drawings from Edelin, 1993). In some cases the limit (arrow) between two growth units is indicated by a decrease in the pith diameter (Carapa procera, C; drawings from Edelin, 1993) and/or even by pith structure as in Juglans sp. (D). G.U., growth unit; ‘n’, ‘n + 1’, successive theoretical years of growth; p, plain pith; s, septate pith.
