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| Bryophytes |
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| Bryophytes are a group of simple and primitive plants. They grow in moist and shady places forming a dense mass or mat on damp soil, rock, logs and other substrata. They are basically terrestrial forms, but require the presence of water for completing the life cycle. Hence, they are commonly described as 'amphibians of the plant kingdom'. |
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| The life cycle of bryophytes shows two distinct phases namely a haploid gametophytic phase and a diploid sporophytic phase alternating with each other. The adult plant body represents the gametophyte. A short-lived sporophyte occurs as a parasite on the gametophyte. |
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| It is the adult plant body in bryophytes. It is either thalloid or in the form of a leafy shoot with stem-like and leaf-like structures. Roots are absent and instead thread-like rhizoids are present. Vascular tissues xylem and phloem are absent. Water and food are directly transported from a cell to cell. |
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| Vegetative reproduction may sometimes occur by fragmentation. However, sexual reproduction is common and is of oogamous type. The mature gametophyte bears male reproductive organs called antheridia and female reproductive organs called archegonia. The antheridia have a club-shaped body and a stalk. They produce flagellated male gametes called antherozoids or sperms. The archegonia are flask-shaped with a well-defined venter and neck. The venter encloses a venter canal cell and an egg cell while the neck encloses a variable number of neck canal cells. |
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| The antherozoids liberated from antheridia, swim in a film of water and reach the archegonia. They are attracted into the archegonia to bring about fertilisation. The zygote develops into the sporophyte. |
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| fig. 8.28 - Life Cycle of
Moss (A Bryophyte) |
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| Zygote represents the first cell of the sporophytic phase. It divides and develops into a sporophytic plant body called sporogonium. The wall of venter forms a protective covering to the sporogonium, called calyptra. Most often, the sporogonium is differentiated into a foot, a seta and a capsule. It remains attached throughout its life to the gametophytic host with the help of foot. It absorbs nutrients directly from the gametophyte. The sporogonium produces haploid spores (meiospores) which get released from the capsule. The spores represent the first cells of gametophytic generation. They germinate to produce new gametophytes either directly or through a juvenile stage called protonema. |
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| The division Bryophyta has been divided into three classes namely: |
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| Hepaticae - Commonly called Liverworts |
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| Anthocerotae - Commonly called Hornworts |
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| Musci - Commonly called Mosses. |
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| fig. 8.29 - Common Examples of Bryophytes |
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