Leaves Reveal Themselves for the First Time
Sam Holloway (UCB)

Canon PowerShot A80 digital camera attached to a Zeiss Stemi 2000-C dissecting microscope
Many plant lineages have "leaves," but leptosporangiate ferns, like this Asplenium, are some of the first land plants to have megaphyll leaves, the same sort of leaves we see in many of the modern plants all around us. For example, flowering plants and conifers have megaphyll leaves, each with a complex network of vascular tissue. Lycopods (with their microphyll leaves having only a single vascular bundle), mosses, hornworts and liverwort (none of which technically has leaves) do not have megaphyll leaves. In this photo we see this plant's first leaflets growing out of a fiddlehead, which will soon unwind itself and proudly display its foliage to the world.