In this article we will discuss about the various examples of bryophyta.
The Bryophyta is such a distinctive group of plants that it may easily be considered as a definite division of the Plant Kingdom. It is, again, phylogenetically so different from the Thallophytes and the Trachaeophytes that it is considered by some as a definite subkingdom parallel to the two others and named Bryophytae (the ending —phytae distinguishes it from the division endingphyta).
The Bryophyta then becomes the single division of the subkingdom Bryophytae. As against this, we have the view of Cronquist, Takhtajan, Zimmermann and others that the Bryophytes being possibly reduced from some higher form, should not be separated from the Trachaeophytes. It may at least be said that, representing a line of evolution of the Land Plants like the Pteridophytes, they deserve a parallel position.
Within the Bryophyta, again, two types of plants, Hepatics or Liverworts (from their imaginary similarity with the liver and the consequent supposed property of curing liver diseases in medieval medicine; Greek hepatos— liver) with dorsiventral differentiation and Musci or the mosses which usually show radial symmetry.
In classical taxonomy Hepaticae and Musci are considered as two classes under the Bryophytes. This position has been retained even in the 1954 edition of Jingler’s Syllabus der Pflanzenfamilien.
Cavers (1910—11) suggested that the Bryophytes be divided into ten groups of equal rank:
I. Sphaerocarpales.
II. Marchantiales.
III. Jungermanniales.
IV. Anthocerotales.
V. Sphagnales.
VI. Andreaeales.
VII. Tetraphidales..
VIII. Polytrichales.
IX. Buxbaumiales.
X. Eubryales.
But, this ignores the, difference between the Hepaticae and the Musci which attitude does introduction to the brvophyta not seem to be justified. The differences between the two groups are so great that same modern taxonomists want to raise the two groups to two subdivisions or even divisions. Bold (1956) suggested Hepaticophyta and Bryophyta (Musci) as two divisions.
Leaving aside this question, most modern Bryologists, beginning from Howe (1899) and Campbell (1918), are almost unanimous that the Anthocerotae, formerly included within the class Hepaticae, are sufficiently distinctive to be raised to the status of a class so that three classes, Hepaticae, Anthocerotae and Musci, are recognized within the division Bryophyta.
These class names are changed to Hepaticopsida, Anthocerotopsida and Bryopsida in accordance with the International Code of Nomenclature which recommends that class names should end in the suffixpsida.
Class Hepaticopsida (Hepaticae):
Dorsiventrally differentiated (sometimes radial and erect) gametophytes which are either simply thallose or with leaf-like appendages (foliose) and are always nerveless. Internal tissues are homogeneous or differentiated. Sex organs borne terminally or developed from superficial dorsal cells.
Sporophyte simple or differentiated into foot, seta and capsule—always of limited growth. Sporogenous cells of endothecial origin and without any columella.
Class Anthocerotopsida (Anthocerotae):
Gametophyte dorsiventrally differentiated, simple and not foliose,. internal tissue homogeneous.
Sex organs embedded in gametophyte—female formed from superficial and male from -hypodermal dorsal cells. Sporophyte differentiated into capsule and foot. Lower part of capsule remains meristematic so that the growth of the sporophyte is not limited. Sporogenous dells of amphithecial origin (with exceptions in Noto thy las’), all internal cells forming a sterile columella.
Class Bryopsida (Musci):
Gametophyte, after a distinct though usually short protonema phase, develops erect shoots, usually of radial symmetry, with leafy appendages (phyllids) on stem-like caulids. Sexual organs develop from superficial cells at the top of apical or axillary meristems.
Sporophyte of limited growth, usually differentiated into foot, seta and capsule. Sporogenous cells of endothecial or amphithecial origin but always (with rare exceptions) surrounding a columella.