CLASSIFICATION OF BRYOPHYTES

UDAY SHANKER

UNIVERSITY DEPARTMENT OF BOTANY,

MAGADH UNIVERSITY, BODH GAYA

DIAGNOSTIC FEATURES OF BRYOPHYTA

Simplest and most primitive members of the

Embryophyta.

Occupy a position intermediate between Algae

and Pteridophytes.

A true root absent. In some members hair-like

rhizoids present.

Vascular tissues are completely absent.

Gametophytes thallose or foliose.

Sexual reproduction highly oogamous.

Male sex organ, the antheridium producing single celled

motile antherozoid.

Female sex organ, the archegonium with a large non-

motile female gamete, the egg (oosphere).

Calyptra present.

External water essential for fertilization.

Embryo develops into a multicellular sporophyte.

Sporophyte (sporogonium) distinct into a foot, a seta and

a terminal spore –producing capsule. Foot and seta absent

in Riccia.

Life-cycle shows heteromorphic alternation of

generations.

Classification of Bryophytes

Schimper (1879) gave Bryophyta the rank of a

division.

It includes about 24,000 spp. grouped in about 960

genera.

Divide into three classes:

i. Hepaticopsida

ii. Anthocerotopsida

iii. Bryopsida

Hepaticopsida About 280 genera and approximately 9,500 spp.

Popularly called liverworts.

Gametophyte either a thallose or foliose.

Internal differentiation into photosynthetic and storage regions.

Photosynthetic cells with numerous chloroplasts but without pyrenoids.

Rhizoids both smooth walled and tuberculated.

Sex organs develop from single initial cell.

Sporogonium simple/with a foot and capsule/with a foot, seta and capsule.

Contd.

HEPATICPSIDA

Archesporium develops from endothecium of the embryo.

Sporogenous tissue differentiates into spore mother cells and elaters (absent in Riccia).

Elaters single celled with spirally thickened walls.

Capsule lacks columella.

Capsule splits along preformed lines of weakness.

Divided into four orders (Cavers, 1910, Campbell, 1936).

i.Sphaerocarpales

ii. Marchantiales

iii. Jaungermanniales

iv. Calobryales.

Hepaticopsida

Sphaerocarpales

Gametophyte leafy and consists of an axis bearing two rows of alternately inserted lobes of “leaves”.

Development and structure of sex organs as well as structure of sporophyte similar to those of Marchantiales.

Chief diagnostic feature is the presence of a globose or flask- shaped envelope (involucre) around each of the sex organ.

Two families :

• Sphaerocarpaceae with two genera Sphaerocarpos and Geothallus.

• Riellaceae with single genus Riella.

Marchantiales

Gametophyte a prostrate, dorsiventral dichotomously branched thallus.

Well marked specialization of tissues with ventral storage and dorsal photosynthetic regions having air chambers and air pores.

Scales and rhizoids (smooth walled and tuberculated) present on ventral surface of thallus.

Sex organs either scattered along the midrib or grouped in receptacles on vertical stalks antheridiophores and archegoniophores.

Capsule wall 1-layered.

Capsule never opens by 4-regular valves.

Consists of about 35 genera and about 420 spp.

Five families :

Family 1. Ricciaceae :

• Sporophyte consist solely of a capsule.

• There are 03 genera and some 140 .

• Oxymitra (Tesselina), Ricciocarpus and Riccia.

Family 2. Corsiniaceae:

• Sporophyte with a capsule and foot.

• Of 03 genera, Corsinia is the best known.

Family 3. Targionaceae:

• Female receptacle enclosed by a sheath (involucre) developed from tissues lateral to it.

• 03 genera : Targionia, Cyathodium and Aitchinsoniella

Marchantiales

Family4. Marchantiaceae :

• Sporophyte with a foot, seta and capsule having typical sterile cells , the elaters, inside the capsules.

• There are 23 genera and some 250 spp .

• Marchantia, plagiochasma, Conocephalum, Dumortiera.

Family 5. Monocleaceae:

• Presence of unique hood-like sheath posterior to the female receptacle.

• Elongate capsule also of different shape from other families of Marchantiales.

• Single Genus Monoclea.

Jungermanniales

• Includes about 244 genera and about 9,000 spp.

• Gametophytes a simple thallose or may be foliose and differentiated into stem and leaves.

• Little internal differentiation of tissues.

• Scales often absent and rhizoids always smooth-walled.

• Antheridium globose or subglobose usually borne on a long stalk.

• Archegonial neck composed of five vertical rows of cells and neck almost as broad as the venter.

• Capsule wall more than 1-layered.

• Mature capsule dehisces longitudinally into four parts.

Jungermanniales Divided into two sub-orders:

i. Metzgerineae (Jungermanniales Anacrogynae) in which the apical cell of a gametophyte does not develop into an archegonium.

Jungermannineae (Jungermanniales Acrogynae), in which the apical cell of branch/main stem develops into an archgonium.

Metzgerineae includes about 20 genera and 500 species.

Evans (1939) recognised the following families in Metzgerineae:

• Treubiaceae

• Fossombroniaceae

• Pelliaceae

• Blasiaceae

• Pallaviciniaceae

• Metzgeriaceae

• Riccardiaceae

• Monocleaceae

Jungermannineae comprise about 80% of the Hepaticopsida with about 220 genera and 8500 species.

Jungermannineae (Jungermanniales Acrogynae), in which the apical cell of branch/main stem develops into an archgonium.

Evans (1939) recognised 17 families.

Representative genera are Porella (Porellaceae) and Frullania (Frullaniaceae ).

Calobryales

• Gametophytes erect leafy with leaves in three vertical rows and all approximately alike.

• Antheridia ovoid, stalked, borne at the apex of axis and develop in a distinct manner.

• Archegonial neck composed of four vertical rows of cells and neck almost as broad as the venter.

• Capsule elongated with 1-layered wall except at the apex.

• There is but only one family , the Calobryaceae with two genera Haplomitrium and Calobryum.

Anthocerotopsida

• Gametophytes dorsi-ventral , lobed thallus without any internal differentiation.

• Ventral scales absent and rhizoids only smooth-walled.

• No air-chambers or air pores.

• Thallus cell with a single laminate chloroplast having a compound pyrenoid.

• Antheridia single or in groups in antheridial chambers .

• Sporogonium with a bulbous foot, a meristematic region and a long cylindrical capsule.

• Capsule wall rich in chlorophyll.

• Capsule with a central collumella.

• Archesporium derived from amphithecium.

Anthocerotopsida

• Capsule contains spores and simple or compound sterile cells with or without spiral thickening.

• Capsule dehisces into two valves which show hygroscopic twisting.

• Single order Anthocerotales with a single family Anthocerotopsida.

• Universally accepted genera are Anthoceros, Megaceros, Dendroceros and Notothylas.

Bryopsida

• Includes about 660 genera and 14,500 species.

• Gametophytes differentiated into two stages- a prostrate, filamentous protonema and an erect,leafy gametophore.

• Gametophore consists of ‘stem’ and spirally arranged ‘leaves’ and bear sex organs.

• Rhizoids multicellular with oblique septa.

• Sex organs formed from the superficial cell of the gametophore.

• Sporogonium determinate and consists of a foot, seta and capsule.

• Capsule wall multi-layered covered by an epidermis with ‘stomata’.

Bryopsida

• Capsule with a central columella.

• Archesporium derived from endothecium or amphithecium.

• Elaters conspicuously absent.

• Bryopsida divided into 3 sub-classes:

• I. Sphagnidae

• II. Andreaeidae

• III.Bryidae.

Sphagnidae

• Commonly called ‘bog mosses’ or ‘peat mosses’.

• Protonema broadly thallose.

• Leaves without a mid rib and composed of narrow ,living, green cells and large, hyaline ,dead cells.

• Antherdia borne in axils of ‘leaves’.

• Archegonia are terminal.

• Archesporium derived from amphithecium.

• Capsule opens by an operculum, but lacks peristome.

• Sporogonium elevated by a pseudopodium of gametophytic origin.

• Single order Sphagnales with a single family Sphagnaceae and single genus Sphagnum of about 336 species.

Andreaeidae

• Commonly called ‘granite mosses’.

• Protonema thallose.

• Archesporium and columella derived from the endothecium.

• Spore sac dome shaped and overarches the columella.

• Antheridia borne in axils of ‘leaves’.

• Pseudopodium present.

• Longitudinal dehiscence of the capsule in four valves.

• Single order Andreaeales with a single family Andreaeaceae with two genera Andreaea (120 spp.) and Neuroloma (monotypic).

Bryidae • Commonly called ‘true mosses’.

• Includes about 14000 species grouped in about 675 genera and 14 orders.

• Protonema filamentous.

• ‘Leaves’ with a midrib more than 1-cell in thickness.

• Sporophyte not elevated by means of pseudopodium, but by elongation of seta.

• Archesporium derived from the endothecium and does not overarch the columella.

• Spore sac separated from the capsule wall by an intercellular space traversed by filament of cells.

• Operculum and peristome present in capsule in a large number of genera.

• Common genera : Funaria, Buxbaumia, Polytrichum.

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