Classification of Bryophytes

Braun for the first time in 1864 introduced the term 'bryophyta' and included algae, fungi, lichens and mosses together in this group. Later, algae, fungi and lichens were separted from the Bryophyta and kept under Thallophyta. Bryophyta retained liverworts and mosses. Group Bryophyta was raised upto the rank of division by Schimper in 1879.

---

Eichler system (1883)

Eichler (1883) divided Bryophyta into groups.

• Group I: Hepaticae
• Group II: Musci

---

Engler system (1892)

Engler (1892) raised Hepaticae and Musci as two classes and divided each class into the three orders.

• Division: Bryophyta
  • Class 1: Hepaticae
    • Order 1: Marchantiales
    • Order 2: Jungermanniales
    • Order 3: Anthocerotales
  • Class 2: Musci
    • Order 1: Sphagnales
    • Order 2: Andreaeales
    • Order 3: Bryales

---

Howe system (1899)

By virtue of distinct characters of Anthoceros and related genera, Howe (1899) raised the order Anthocerotales to the rank of a class and divided Bryophyta into three classes.

• Division: Bryophyta
  • Class 1: Hepaticae
  • Class 2: Anthocerotes
  • Class 3: Musci

Howe (1899) system of classification was followed by Smith (1938, 1955), Takhtajan (1953), Wardlaw (1955) and Schutser (1958) but they preferred to call class Anthocerotes as Anthocerotae.

• Division: Bryophyta
  • Class 1: Hepaticae
  • Class 2: Anthocerotae
  • Class 3: Musci

International code of Botanical Nomenclature (ICBN) in 1956 suggested suffix-opsida for the classes rank. However, Rothmaler has already proposed this for the classes of Bryophyta in 1951.

• Division: Bryophyta
  • Class 1: Hepaticae as Hepaticopsida
  • Class 2: Anthocerotae as Anthoceropsida
  • Class 3: Musci as Bryopsida

Proskauer (1957) suggested that the class name Antheoceropsida should be written as Anthocerotopsida. Parihar (1965) and Holmes (1986) followed Proskauer’s system of classification. Accordingly Bryophyta was devided into three classes.

• Division: Bryophyta
  • Class 1: Hepaticopsida
  • Class 2: Anthoceropsida as Anthocerotopsida
  • Class 3: Bryopsida

---

Class 1: Hepaticopsida

General Characters

'Hepaticopsida' is derived from Latin word 'Hepatica' = liver. Hence, plants of this class are also know as liverworts.

Liverworts includes about 280 genera and 9500 species.

Main plant body is either thalloid or foliose.

Thalloid plants are lobed, prostrate, dorsiventral and dichotomously branched.

Foliose plants are leafy, entire, lobed and withouf midrib arranged in two to three rows on the axis.

Rhizoids are unicellular and branched.

Many chloroplasts are present in single cell and pyrenoid is absent

Liverworts may be monoecious or dioecious

Sex organs develop dorsally or apically and either superficial or embedded in gametophytic tissues.

Sporophyte is simple represented by capsule only (Riccia) or differentiated into foot seta and capsuel (Marchantia).

Archesporium originates from endothecium

Sporogenous tissues develop either in spores only (Riccia) or differentiated into sterile elater mother cells and fertile spore mother cells.

Elaters are unicellular with spiral thickenings and are hygroscopic in nature

No columella is found in the capsule

Capsule wall is one to few layered lacking stomatal pores

Capsule dehiscence may be either irregular or through definite number of valves.

Spores germinated into gametophytic plant body.

Liverworts exhibit hetermorphic alternation of generation.

---

Class 2: Anthocerotopsida

General Characters

Members of anthocerotopsida are also known as 'hornworts' because of resemblance of sporophyte with horn.

Hornworts includes about 6 genera and 300 species.

Main plant body is gametophyte, flat, lobed and dorsiventral.

Rhizoids are smooth-walled only.

Scales are simple only.

Thallus is not differentiated into photosynthetic and storage zone.

Air chambers and air pores are absent

Single cgloroplast with single pyrenoid is present in each cells.

Mucilage cavities are present, which open on the ventral surface through slime pores.

Sex organs are embedded in the thallus.

Single or a number of antheridia borne in cavities so called antheridial chambers.

Sporophyte is differentiated into foot, meristematic zone and capsule.

Because of the presence of meristematic zone, sporophyte shows indeterminate growth.

Archesporium develops from amphithecium.

Sporogenous tissues develop into fertile spores sterile pseudoelaters.

Elaters are multicellular without any spiral thickenings, hence called pseudoelaters.

Columella is found in the center of capsule.

Capsule wall is four to six layered and epidermis has stomata.

Capsule matures from apex to base and dehisce by two valves.

---

Class 3: Bryopsida

General Characters

Members of Bryopsida are also known as 'Mosses.

Bropsida is the largest class of Bryophyta. It includes about 700 genera and 14000 species.

Main plant body is gametophyte, which is differentiated into juvenile protonema and adult leafy gametophore.

Protonema develops by germination of spores.

Gametophore are leafy branches developed on protonema.

Gametopgores are differentiated into rhizoids, stem (axis) and leaves.

Leaves are un-lobed, with midrib and spirally arranged in 3 to 8 rows in the axis.

Rhizoids are multicellular, branched with oblique septation.

Axis is differentiated into central conducting strands surrounded by cortex.

Sex organs are borne apically in clustures on axis.

Sporophyte develops on the gemetophyte and differentiated into foot, seta and capsule.

Seta is rigid and long.

Sterile columella is developed from endothecium.

Archesporium give rise to spores only.

Elaters and pseudoelaters are absent.

Capsule dehisce by means of lid or operculum.

Peristome teeth help the spore dispersal.

Spores germinate into juvenile protonema.

---

First published on 13-04-2021
Last updated on 01-05-2021

---

See also

• General characteristics
• Affinites of bryophytes
• Classification of bryophytes
• Riccia:
  • General characteristics
  • Reproduction