General Characteristics of Bryophytes
Imagine a plant that never quite left the water behind. It lives in damp, shady places — on wet rocks, along stream banks, under forest trees. It is small, soft, and green, hugging the ground. This is a bryophyte: moss, liverwort, or hornwort. Biologists call them the "amphibians of the plant kingdom" because, like frogs, they live on land but still depend on water for one critical step in their life cycle.
The Intuition: Why They Are "Amphibians"
Think about what a fully terrestrial plant needs. A rose bush, for example, has roots that pull water from deep soil, a stiff stem with tubes (xylem and phloem) to carry that water upward, and a waxy cuticle to prevent drying out. It produces pollen that travels through air, so it never needs a drop of water to reproduce.
Bryophytes do none of that. They have no true roots — only thin, hair-like rhizoids that anchor them but do not absorb water efficiently. They have no vascular tissue — no xylem or phloem — so water must move from cell to cell by osmosis and capillary action. That is painfully slow and works only over very short distances. That is why bryophytes stay small, rarely taller than a few centimetres. They cannot stand tall and dry; they must stay moist.
And then there is reproduction. The male gamete (sperm) is flagellated — it must swim through a film of water to reach the egg. No water, no fertilisation. That is the amphibian link: the body is adapted to land, but the reproductive act still belongs to water.
The Precise Statement
Bryophytes are non-vascular, embryophyte plants with a dominant gametophyte generation. The plant you see — the green, leafy mat — is the haploid gametophyte. It is the main, photosynthetic, long-lived phase. The sporophyte is small, dependent, and attached to the gametophyte for its entire life.
Dominant generation: Gametophyte (haploid, n)
Sporophyte: Dependent on gametophyte (diploid, 2n)
Key Characteristics in Detail
1. Habitat and Structure
They grow in moist, shaded environments. The body is a thallus — a flat, undifferentiated sheet — or a leafy shoot with no true roots, stems, or leaves. Rhizoids are unicellular (in liverworts) or multicellular (in mosses) but never conduct water.
2. Vascular Tissue: Absent
No xylem or phloem. Water moves by diffusion and capillary action along the surface. This limits height and restricts them to wet places.
3. Life Cycle: Alternation of Generations
The gametophyte produces male and female reproductive organs — antheridia (sperm) and archegonia (eggs). Fertilisation requires water. The resulting zygote grows into a sporophyte that remains physically attached to the gametophyte, drawing nutrition from it. The sporophyte produces spores via meiosis, which germinate into new gametophytes.
In all higher plants (ferns, gymnosperms, angiosperms), the sporophyte is the dominant, independent generation. Bryophytes are the reverse: the green plant you see is haploid.
4. Water for Fertilisation
The sperm are biflagellate and swim to the archegonium. Even a thin film of dew or rainwater is enough. This is the single most important ecological constraint — bryophytes cannot colonise dry land.
5. No True Roots, Stems, or Leaves …