Bryophytes are mostly semi-terrestrial; grow in moist and shady places. They form green mats on damp soil, rocks, walls and tree trunks, especially during rainy season.
Some are aquatic (e.g. Riella, Riccia fluitans), a few grow as epiphytes (e.g., Porella, Dendroceros) and some known to be saprophytes (e.g., Buxbaumia aphylla, a moss; Cryptothallus mirabilis, a liverwort).
2. Life cycle:
Haplodiplontic type, characterized by heteromorphic alteration of generation and sporogenic meiosis.
3. Dominant Plant Body:
Gametophyte is the dominant plan t body which is green long-lived and independent. The gametophyte is a thallus consists of rhizoids, axis (=stem) and leaves.
4. Absence of Vascular Tissues:
Bryophytes have no vascular tissue for conduction of water and food. In place of xylem it carries Hadrome & in place of Phloem it carries Leptome. Arrangement is Hadrocentric.
Rhizoids are unicellular or multi-cellular root-like structures for absorption and anchorage. True roots absent.
6. Vegetative reproduction:
It takes place by various methods like:
(a) Death and decay old parts of the thallus,
(b) By adventitious branches, or
(c) By special structures like tubers, gemmae (produced in gemma cups, e.g., Marchantia) and protonema.
7. Sexual reproduction:
The sexual reproduction is oogamous type, i.e., the fusion of non-motile egg with motile biflagellate antherozoid (male gamete) form a diploid zygote.
8. Sex organs:
Sex organs are multi-cellular and jacketed i.e. protected by sterile cell layer. They are of 2 types, i.e. antheridia (Club-shaped male sex organs) and archegonia (flask-shaped female sex organ). Antheridium has a short stalk with ovoid or club-shaped body.
The body filled with androcyte mother cells. Each androcyte mother cell diagonally divides into 2 androcytes and each androcyte metamorphosed into a biflagellate male gamete called antherozoid. Archegonium consists of a short stalk, flask-shaped venter and a tubular neck. Venter is 1-2 layered and encloses two cells i.e. an egg and a venter canal cell. Neck is single layered and encloses 5- 6 rows of cells.
Water is essential for fertilization as a medium for transport of antherozoids to reach at archegonia. Fertilization results are the formation of diploid zygote which retains in the venter of archegonium for further development.
The zygote is the first cell of sporophyte generation. The zygote develops into a multi-cellular embryo which stays for short duration and then develops into a sporophyte. Because of embryo formation bryophytes are included in Embryophyta.
The sporophyte of a bryophyte is called sporogonium which consists of foot, seta and capsule. The sporogenous cells of capsule develop into spore mother cell after repeated divisions.
Each spore mother cell undergoes meiosis to form four haploid spores. Thus, the spores produced inside the capsule of bryophytes are meiosporcs and homosporous similar types). A spore is the first cell of gametophyte generation. In liverworts, spores germinate into young gametophyte. However, in mosses each spore germinates into a juvenile stage called protonema, from which erect gametophores (adult gametophytes) develop.