Figure A1.

Phylogeny of land plants. The land plants (embryophytes) can be divided into four groups. The bryophytes are a paraphyletic group comprised of the three earliest diverging lineages of land plants, i.e., the liverworts, mosses, and hornworts. The next group to diverge is the monophyletic lycophytes that consists of clubmosses, quillworts, and spikemosses and further up the tree the ferns represent a lineage diverging just before the emergence of seed plants. The seed plants are divided into two groups, the gymnosperms and the angiosperms (flowering plants). Within the angiosperms Amborella is thought to be the earliest diverging genus. Arrows indicate important morphological changes during the evolution of land plants.