Classification of Bryophytes by Proskauer (1957) (With Simple Diagram)

In this article we will discuss about classification of bryophytes by Proskauer (1957) :- Hepaticopsida (Liverworts), Anthocerotopsida (Hornworts) and Bryopsida (Mosses)

Classification of Bryophytes by Proskauer

• According to Proskauer (1957) the division Bryophyta is categorized into three classes: Hepaticopsida, Anthocerotopsida and Bryopsida.
• The classes Hepaticopsida and Anthocerotopsida are subdivided into various orders, while Bryopsida is divided into a subclass, which is then further divided into orders.
• Parihar (1965) and Holmes (1986) followed classification of bryophytes by proskauer.

Division: Bryophyta

• They are green and have chloroplasts.
• The plant body is not differentiated into true roots, stem and leaves.
• The dominant plant body is gametophytic.
• Vascular tissue are completely absent.
• Sexual reproduction is oogamous and reproductive organs are multicellular and jacketed.
• The division bryophyta is divided is into three major classes: Hepaticopsida (Liverworts), Anthocerotopsida (Hornworts) and Bryopsida (Mosses)

Class 1: Hepaticopsida (Liverworts)

• The plant body in the gametophyte stage is either thalloid or foliose.
• The thalloid gametophytic body is prostrate, lobed, dorsiventral and dichotomously branched.
• In foliose forms, the leaves are entire, lobed or divided, lacking a midrib and are arranged in two to three rows along the axis.
• The rhizoids present are unicellular and lack of septa.
• Each cell within the thallus is contain many chloroplasts, which do not contain pyrenoids.
• The reproductive organs are embedded on the dorsal surface.
• The sporophyte may be simple (Riccia) consist of capsule only or it may be more complex, differentiated into foot, seta and capsules (Marchantia, Pallia, and Porella)
• The sporogenous tissue derived from the endothecium of an embryo and can either produce only spores (Riccia) or differentiate into sterile elater mother cells and fertile spore mother cells.
• Elaters are unicellular, hygroscopic and possess spiral thickenings.
• The capsule lacks a columella and its wall can be one to several layers thick, without the presence of stomata.
• This class is further divided into four orders: Sphaerocarpales, Marchantiales, Jungermanniales, and Calobryales.

Class 2: Anthocerotopsida (Hornworts)

• The gametophytic plant body is flat, dorsiventral, thalloid and lobed.
• Anatomically, the thallus is not differentiated into distinct zones.
• In gametophytic plant body, there are no air chambers or air pores present.
• Each cell within the thallus is contain a single chloroplast, which may contains one or multiple pyrenoids.
• The reproductive organs are embedded within the thallus.
• The sporophyte is cylindrical and is partly dependent on the gametophyte for nourishment. It is differentiated into foot, meristematic zone (seta) and capsule.
• The sporogenous tissue derived from the amphithecium of the embryo, while the endothecium plays a role in formation of columella.
• This sporogenous tissue is responsible for producing fertile spores and sterile elaters, which lack spiral thickenings and are referred to as pseudo elaters.
• The capsule wall consists of four to six layers, with the epidermis containing stomata.
• This class includes only one order: Anthocerotales.

Class 3: Bryopsida (Mosses)

• The gametophytic plant body is differentiated into two distinct stages: the juvenile stage and the leafy stage, also known as the gametophore.
• The juvenile stage is green, filamentous, branched and also known as protonema, which arises from the germination of spores.
• The leafy stage (Gametophores) consists of upright leafy branches that develop from the protonema.
• These gametophores may be either branched or unbranched and are composed of three main parts: rhizoids, a stem (axis) and leaves (Phyllids).
• The leaves possess a midrib, are unlobed, and are arranged spirally in three to eight rows along the axis.
• Rhizoids are multicellular, filamentous, branched structures with oblique septa.
• The reproductive organs develop from the superficial cells of the gametophore.
• The sporophyte is green and can be divided into three parts: the foot, seta, and capsule.
• The capsule wall has stomata at several places.
• A columella is typically present and originates from the endothecium.
• Elaters are absent and peristome plays a crucial role in the dispersal of spores.
• The class Bryopsida is further subdivided into three subclasses: Sphagnidae, Andreaeidae, and Bryidae.