CO 20

Fig. 20.1

Fig. 20.2

Outline Introduction Phylum Hepaticophyta - Liverworts Leafy Liverworts Phylum Anthocerophyta - Hornworts Phylum Bryophyta - Mosses

Introduction About 23,000 species of bryophytes. Include mosses, liverworts, and hornworts. Habitats range in elevation from sea level up to 5,500 m or more. Bryophytes of all phyla often have mycorrhizal fungi associated with their rhizoids. In some instances, fungi apparently are at least partially parasitic.

Introduction Peat mosses are ecologically important in bogs. Luminous mosses are found in caves and in other dark, damp places. None have true xylem or phloem. Many have hydroids. Exhibit alteration of generations.

Phylum Hepaticophyta Liverworts Structure and Form Most common liverworts have flattened, lobed thalli. Gametophyte stage develops from spores. When spores germinate they may produce immature gametophyte (protonema).

Phylum Hepaticophyta Thalloid Liverworts Best known species are in the genus Marchantia. Thick thallus that forks dichotomously as it grows. Consists of parenchyma cells with few, if any, chloroplasts.

Fig. 20.5

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Fig. 20.6b

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Fig. 20.6c

Asexual Reproduction of Marchantia

Leafy Liverworts Always have two rows of partially overlapping “leaves” whose cells contain distinctive oil bodies. Often have folds and lobes. Archegonia and antheridia are produced in cup-like structure. At maturity, sporophyte capsule may be pushed out as the seta elongates. Germinating spore produces a protonema.

Fig. 20.8

Phylum Anthocerophyta Hornworts Structure and Form Mature sporophytes look like miniature greenish-blackish rods. Only about 100 species worldwide. Thalli have pores and cavities filled with mucilage, that often contain nitrogen-fixing bacteria.

Fig. 20.9a

Hornwort Sporophyte

Hornworts Asexual Reproduction Fragmentation Separation of lobes from thallus. Sexual Reproduction Archegonia and antheridia are produced in rows beneath the upper surface of the gametophytes. Have both unisexual and bisexual plants.

Phylum Bryophyta Mosses Structure, Form, and Classes About 15,000 species of mosses currently known. Divided into three classes: Peat Mosses True Mosses Rock Mosses

Mosses “Leaves” of moss gametophytes have no mesophyll tissue, stomata, or veins. Blades are nearly always one-cell thick, and are never lobed or divided. Initially formed in three ranks and usually end up appearing to be arranged in a spiral or alternately on an axis that twists as it grows. Sexual Reproduction:

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Fig. 20.13c

Fig. 20.13a

Fig. 20.13b

Phylum Bryophyta Human and Ecological Relevance Pioneer Species of Primary Succession Indicators of Surface Water Packing Material Peat Mosses Soil Conditioner Poultice Material Fuel

Review Introduction Phylum Hepaticophyta - Liverworts Leafy Liverworts Phylum Anthocerophyta - Hornworts Phylum Bryophyta - Mosses