Pteridophyta

Pteridophyta is a division of non-seed vascular plants that includes ferns and their close relatives, such as horsetails and whisk ferns. Members reproduce by spores rather than seeds or cones. They possess vascular tissue (xylem and phloem) and typically have a sporophyte-dominant life cycle, with a free-living, photosynthetic sporophyte and a separate, often smaller gametophyte.

Life cycle: Pteridophytes exhibit alternation of generations. The diploid sporophyte produces spores in sporangia. In many ferns, sporangia are aggregated into sori on the undersides of fronds and may be protected by an indusium. The haploid gametophyte (gametophyte or prothallus) is usually independent and short-lived; it bears motile sperm and archegonia or antheridia and requires free-standing water for fertilization.

Morphology: Fronds (leaves) can be large and divided in many ferns; new fronds emerge coiled as fiddleheads. Rhizomes often spread horizontally; some have scale-like features. Horsetails have hollow, jointed stems with whorls of leaf-like structures; whisk ferns are usually simple, with reduced roots and stems.

Ecology and distribution: Pteridophytes are widespread in forests, wetlands, and tropical regions, including drier microhabitats. They depend on moist conditions for fertilization, though some species tolerate dryness. They play roles in soil stabilization and as understory components, and they are used ornamentally and as model organisms in studies of plant evolution and development.

Taxonomic note: Traditionally a single division, modern classifications sometimes split Pteridophyta into multiple lineages (e.g., Polypodiopsida, Equisetopsida, Psilotopsida) or place ferns, horsetails, and whisk ferns in a clade separate from lycophytes.