Liverworts

Gametophyte (=gamete-forming phase)

Vegetative features

• Dominant, free-living generation and photosynthetic phase

  • Chloroplasts are small and many (like mosses, unlike hornworts)

  • Unlike other plants, the liverworts possess oil bodies in their stems and leaves, which can be used as structures to store toxic chemicals (Romani et al., 2022) 

Stems or axes

• Thalloid liverworts have a "stem" that is flattened and algae-like

• Leafy liverworts have a more cylindrical stem with leaves attached in two rows

Leaves or phyllids

• Leafy and thalloid forms exist (leafy more common than thalloid) 

  • Thalloid liverworts look very algae-like (=thalloid), and there is no distinction between leaf and stem

  • Leafy liverworts have two rows of small leaves on the ventral surface

• No stomata in liverworts, but the complex thalloid liverworts have open pores (lack guard cells)

Roots or rhizoids

• No true roots, but they have root-like rhizoids

• Do not possess vascular tissue

• Anchor plant, and may absorb small amounts of water

• Unicellular and clear in appearance (compare these to the multicellular and brown rhizoids of mosses) 

Reproductive Features

Asexual reproduction

• Some have the ability to asexually reproduce

  • Possess gemmae, which are pieces of tissue in a cup-like structure

Sexual reproduction

• Antheridia and archegonia emergent / visible from the body (like mosses, unlike hornworts)

• Thalloid liverworts sometimes bear antheridia and archegonia on raised branches (e.g., Marchantia).

  • The egg-producing archegonia are formed in between finger-like projections on a long stalk, called archegoniophores (see image below)

  • The sperm-producing antheridia are formed on the underside of umbrella-like structures called antheridiophores (see image below)