Pterophytes
Pterophyta are the most
successful of the seedless tracheophytes. They have large megaphylls which
grow off an underground rhizome. The have compound leaves, which grow as
the coiled tip of the gametophyte unfurls. The specialized sporophylls have
sporangia on their undersides in clusters called sori. When mature, spores
are catapulted. This mechanism allows spores to go far, but the sperm are
still flagellated. An innovation in ferns is that the archegonia and antheridia
on the gametophyte mature at different times, ensuring cross fertilization
between gametophytes. This can lead to hardier and better adapted species.
Back to:
Phylogenetic Tree
Vascular Plants
Geologic Timeline