Figure 1.

The gymnosperms include four divergent subclasses of land plants: A) Cycadidae (cycads), B) Gnetidae, C) Pinidae (conifers), and D) Ginkgoidae (ginkgo). Photos show a representative species from each subclass (all photos are by the authors). E) Conifers and other gymnosperms have long-lived, tough leaves with relatively low nitrogen concentrations and photosynthetic rates, reflecting their stress-adapted life histories. Leaf economic data for conifer (black symbols) and angiosperm (gray/open symbols) species in the Glopnet database (Wright et al. 2004). Circle = tree, square = shrub, star = herb, cross = graminoid.