Q.Describe the salient features of Bryophyta, including their habitat, plant body organisation, the role of water in reproduction, and their classification into liverworts and mosses.

Habitat. Bryophytes are mostly terrestrial, favouring moist, shaded places, and are important pioneer colonisers of bare rock and soil.

Plant body. The visible plant body is the haploid gametophyte. It lacks true roots, stems and leaves -- instead it has root-like, stem-like or leaf-like structures, anchored by rhizoids (unicellular in liverworts, multicellular in mosses).

Role of water in reproduction. Fertilisation depends on external water: the male sex organ, the antheridium, produces biflagellate, motile antherozoids, which must swim through a film of surface moisture to reach the egg held inside the flask-shaped archegonium. This water-dependence, despite an otherwise terrestrial habit, is exactly why bryophytes are called the 'amphibians of the plant kingdom'.

Generation dominance. After fertilisation, the zygote develops into a multicellular sporophyte that stays permanently attached to, and nutritionally dependent on, the gametophyte. So unlike Pteridophyta and Gymnosperms, it is the gametophyte -- not the sporophyte -- that is the dominant, independent generation in Bryophyta.

Classification -- liverworts. Liverworts (Hepaticeae) are considered the most primitive bryophytes. Their gametophyte is a flat, green, dorsiventral thallus, lying prostrate and anchored by unicellular rhizoids. Example: Riccia, Marchantia.

Classification -- mosses. Mosses (Musci) are more advanced, with a gametophyte that passes through a filamentous protonema stage (enabling vegetative propagation by budding) before developing into an erect leafy stage bearing the sex organs and, eventually, the attached sporophyte (foot, seta, capsule). Example: Funaria, Sphagnum.

Economic importance. Mosses provide food for some animals, Sphagnum yields peat used as fuel, mosses serve as water-retentive packing material, and both liverworts and mosses help colonise bare rock and bind soil against erosion.

Cover habitat, plant-body organisation, the water-dependent fertilisation mechanism, which generation dominates, and finally the two-way classification (liverworts, mosses) with examples, in that order.

• Omitting why bryophytes are called 'amphibians' -- the specific water-dependent fertilisation step, not just a general land+water habitat.
• Reversing generation dominance, i.e. saying the sporophyte is dominant in bryophytes.