Abstract A comparison was made of morphological and chemical differences between sapwood, discolored sapwood (wound-initiated discolorations), and heartwood in Maclura pomifera (Raf.) Schneid. and Robinia pseudoacacia L. The heartwood and discolored sapwood in the vicinity of wounds differed significantly in color, water content, frequency of amorphous deposits, percentage of material soluble in water (hot and cold) and 1% NaOH, ash content, and pH. Hence, when the living cells of the sapwood die as a result of mechanical injury of a type which results in discolored tissue, this tissue, while similar in appearance to heartwood, is not synonymous with heartwood.