This echoes the observation by Cross and Bevan almost a century ago when crystallinity of cellulose was first proposed, “The root idea of crystallography is identical invariability while the root idea of the world of living matter is essential individual variation” (44). Recognizing the species and tissue specificities of the structures of native celluloses is essential to progress in understanding the diversity of cellulose synthases encoded in the genomes of plants and to understanding the even greater diversity of the cellulases produced by species-specific plant pathogens.