The ammo-acid compositions of proteins present in the sapwood and heartwood from three species of Eucalyptus, in normal, reaction, and opposite wood from Pinus radiata seedlings, and in reaction and opposite wood from Eucalyptus goniocalyx, are listed. The question of the location of protein within wood cell walls is discussed. The amounts of tyrosine found in the woods from P. radiata seedlings are incompatible both with the belief that it determines the intensity of staining of reaction wood cell walls with Millon's reagent, and that it is the source of the p-hydroxybenzaldehyde obtained when milled wood lignin is oxidized with nitrobenzene. Loss of amino acids in the presence of milled wood lignin, α-cellulose, hemicellulose, glucose, mannose, galactose, xylose, arabinose, glucuronic, and galacturonic acids is demonstrated. The presence of numerous peaks which are not indentifiable with known amino acids in the chromatograms of wood hydrolysates is believed to be due largely to the products of interaction of amino acids and sugars. Some retention of nitrogen by the residues of wood hydrolysates occurs. The significance of the results obtained with the wood samples listed above is discussed against this background.