As indicated above, none of the various “representations” of lignin structure have ade­quately reflected native macromolecular configuration. Indeed, there may not be any other natural product whose “structure(s)” have been approximated through attempts to de­termine subunit linkage type and frequency, but not through obtaining sequences of the interunit linkages. However, the trends noted through attempts to obtain precise, rigorous, quantification and identification of subunit type, and their frequencies, in lignins present in Arabidopsis and alfalfa are considered indicative, at least by ourselves, of non-random assembly. This is not to say though that all interunit linkages can yet be accounted for — currently, ~40-45% can at best be fully quantified using these methods. In addition, lignin analyses suffer from another limitation: Technologies have not yet been developed to probe precise lignin structures in different cell wall layers and/or in distinct cell wall types (e. g., xylem versus fibers).