Figure 3.

Phylogenetic tree showing the distribution of lignin monomer composition across major lineages. *, S-units are only found in cell cultures of Ginkgo, not in wood (Novo Uzal et al., 2009). **, Lignin-like structures are reported in some mosses and green algae, but the presence of real lignin in these nonvascular species remains questionable; red algae have been barely studied (Weng et al., 2008b; Martone et al., 2009).