Subdivision Bryophytina Engler

Technical introduction

Division: Bryophyta

Description

Morphology and Anatomy

Gametophyte

The gametophyte ranges in size from very small to up to 80 cm length. The shoots arise from a single, usually three faced apical cell (sometimes only two faced). Each daughter cell goes on to form a segment called metamer with a leaf, accompanying axillary hairs and a branch primordium.

General architecture is of a main stem with lateral branches, which occasionally are missing. Branch development follows two types:

• Bryum type: Branch primordium is dormant from the start and thus does not produce leaves.
• Climacium type: Branch primordium produces some small, unfinished leaves, then goes dormant as a now formed bud.

Stem

In a cross section stems often show differentiation into somewhat specialised tissues. The outer layer, called epidermis usually consists of thick-walled cells. Only in hyalodermis thin walled outer cells are observed. The cortex usually comprises of an outer sclerodermis of thick-walled thin lumen sterids and an inner cylinder of parenchyma cells. The innermost central strand consists of hydroids, which in the class polytrichopsia are surrounded by leptoid cells.

In the axils between stem or branch and leaves axillary hairs are found commonly. Their architecture is usually simple: uniserate and filamentous, with a base of one to a few short brownish cells topped by one to more than ten hyaline cells. Pseudoparaphyllia are usually found at branch primordia and are filamentous or foliose. They can be missing. Paraphyllia usually occur scattered along the whole stem. They are filamentous or formed like a scale or leaf. See however the ongoing discussion about what actually is a true paraphyllia and pseudoparaphyllia, e. g. outlined in Goffinet and Shaw's Bryophyte Biology.

Rhizoid

Leaves

Gametangia

Perichaetia are found in acrocarpous, cladocarpous or pleurocarpous arrangement:

• Acrocarpy: The primary module of a branch gives rise to a single perichaetium at its apex. In some taxons primordia below the apex can develop and continue growth and develop into perichaetia.
• Cladocarpy: Formation of one or more apical perichaetia delegated to lateral branches/secondary or tertiary modules. The primary modules cease vegetative growth. Fertile and vegetative branches look the same.
• Pleurocarpy: Perichaetia are formed by secondary or tertiary modules which usually, but not always, lack branches or branch primordia themselves. The primary branch can continue to grow or stop. Fertile branches can be recognised by their swollen look and differing leaf development.

Pleurocarpy is only found in the subclass of Bryidae.

Protonema

The Protonema consists usually of a one cell thick branched filamentous net. Its life span is reguarly short, it dies when shoots emerge. Rhizoids are found. In rare cases the protonema is thallose or persits.

Sporophyte

Cytology and molecular biology

It is assumed that the basic chromosome number of bryophytina is x = 4. Other reports assume or the class Polytrichopsida x = 7, and for other classes x =6, 7. Derived chromosome numbers range from n = 5 to n = 72 or even n = 96. Common is n = 10-14, in the class Polytrichopsida n = 7, 14, 21. Haplolepideus mosses are frequently n = 12, 13, 14, acrocarpous diplolepideous mosses n =< 9 or n = 10, 11 and pleurocarpous diplolepideous mosses n = 10, 11.

Ecology, Physiology and Distribution

Subtaxa

Literature

1. Engler, Adolf; Frey, Wolfgang; Stech, Michael; Fischer, Eberhard (2009): Bryophytes and seedless vascular plants. 13. ed. Stuttgart: Bornträger (Syllabus of plant families, = Adolf Engeler's Syllabus der Pflanzenfamilien ; Pt. 3).

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