ABSTRACT
Gymnosperms include the earliest living lineages with innovations of a greatly reduced male gametophyte (pollen), pollination as well as seeds, but with extremely large genome. Recent molecular phylogenetic studies indicate that the fi ve major lineages of extant gymnosperms (cycads, Ginkgo, Gnetales, Pinaceae, and all other conifers) form a monophyletic group that is sister to angiosperms, although an alternate placement of Gnetales as sister to the angiosperms cannot be unambiguously rejected. Cycads represent the likely sister lineage to all other extant gymnosperms and are consistently included in comparative developmental and molecular systematic studies. As a basal lineage, cycads provide exemplars to help ascertain the generalized gymnosperm reproductive features from which fl owering plant morphology and genetic controls were likely modifi ed (https://www. greenbac.org/tree.html: The green plant BAC library project).
