New techniques, such as nucleic acid sequencing and refined methods of spectrographic analysis of plant products, have contributed to the continuing vitality of botanical science, and correspondingly the need for a second edition of Green Plants. Sequence analyses have indicated, for example, the evolutionary distance between the mosses and liverworts, the latter appearing closer to the green algae, and presumably to the early colonists of the land. Chemical analyses have revealed surprisingly that the material thought to be sporopollenin coating the membranes of certain green algae, unlike sporopollenin, is largely aliphatic in nature. The evolutionary significance of this discovery is not yet clear, but it is noteworthy that a chemically similar, acetolysis-resistant, material has been found coating the female gamete in archegoniate plants.

Advances in comparative morphology and paleobotany have also been notable. Penetrating studies of sexual reproduction in the Gnetales have thrown fresh light on the origin of double fertilization as it is seen in flowering plants, and has strengthened the view that the endosperm, unique to the angiosperms, is in origin a second embryo, but remains a tissue in which embryogenesis is normally permanently suppressed. The firm evidence, now available, for certain lowly plants from the Rhynie Chert (Lower Devonian) being gametophytes of the rhyniophytes has confirmed the existence of an archegoniate life cycle in these early colonists of the land.