Pteridophyte diversity.

(a) The leafless, rootless green stems of the whisk fern (Psilotum nudum) branch by forking and bear many clusters of yellow sporangia that disperse spores via the wind. The gametophyte of this plant is a tiny, white structure that lives underground in a partnership with fungi. (b) The giant horsetail (Equisetum telmateia) displays branches in whorls around the green stems. The leaves of this plant are tiny, light brown structures that encircle branches at intervals. This plant produces spores in cone-shaped structures, and the wind-dispersed spores grow into small green gametophytes. (c) The early diverging fern Botrychium lunaria, showing a green photosynthetic leaf with leaflets and a modified leaf that bears many round sporangia. (d) The later-diverging fern Blechnum capense, viewed from above, showing a whorl of young leaves that are in the process of unrolling from the bases to the tips. The surrounding older leaves have many leaflets. The stem of this fern grows parallel to the ground and is thus not shown. Most ferns produce spores in sporangia on the undersides of leaves.