Spruce wood meal (Picea pungens), sequentially solvent pre-extracted with water, ethyl ether, and ethanol were subjected to acidolytic delignification treatments of increasing severity, and the lignin sol fractions were analyzed with regard to chemical structure and molecular architecture. Treatments with 0.2 N HCL in 90% aqueous dioxane ranged between 12 hr. at room temperature and 8 hrs. at reflux. The analysis of the dissolved lignin (sol) fractions indicate significant changes in the chemical structures only with regard to aryl-alkyl ether and phenolic hydroxyl content, and with regard to molecular weights and molecular weight distributions. While alkyl-aryl ether content decreases rapidly with acidolysis treatment under reflex conditions, phenolic hydroxyl content increases conversely. Molecular weight increases as delignification procedes. As crosslink density is a function of alkyl-aryl ether content, these results suggest that the 6 7 crosslink density of the sol fraction decreases while molecular weight increases. This contradicts to the theoretical behavior for the degradation of an infinite network and suggests that lignin in wood exists as a gel (network polymer) of extremely low crosslink density or as an ungelled, branched polymer only. Delignification is therefore not controlled by degelation but rather by interaction with carbohydrates via covalent or hydrogen bonds and/or by physical entrapment in the cell wall matrix. This is in accord with earlier hypothesis on the controlling effects of pore structure by Goring et. al. and transient ether linkages by Glasser. / M.S.