capsule
capsule
1. (of prokaryotes) The gelatinous, outer surface layer to the cell (also known as the sheath in cyanobacteria), which is composed primarily of polysaccharides. In pathogenic bacteria, and possibly in others, it appears to serve a protective function against the defensive mechanism of the host, since such bacteria become non-infective in its absence.
2. The spore-bearing structure of a moss or liverwort. In most mosses the capsule may be spherical, cylindrical, oval, or pear-shaped, and is borne on a stalk or seta; the seta in turn is anchored to the gametophyte by an absorptive region called the foot. The capsule is protected, at least initially, by a calyptra. In most cases the capsule has a mouth initially covered by a lid; when the spores inside the capsule are mature, the lid falls off and the spores are released, to be dispersed by wind. (Compare SPHAGNUM and ANDREAEIDAE.) In liverworts the capsule is usually ovoid or spherical and has no lid. On ripening, the capsule usually splits into four ‘valves’, which open out to release the spores.
3. A dry fruit, normally dehiscent.
1. (of prokaryotes) The gelatinous, outer surface layer to the cell (also known as the sheath in cyanobacteria), which is composed primarily of polysaccharides. In pathogenic bacteria, and possibly in others, it appears to serve a protective function against the defensive mechanism of the host, since such bacteria become non-infective in its absence.
2. The spore-bearing structure of a moss or liverwort. In most mosses the capsule may be spherical, cylindrical, oval, or pear-shaped, and is borne on a stalk or seta; the seta in turn is anchored to the gametophyte by an absorptive region called the foot. The capsule is protected, at least initially, by a calyptra. In most cases the capsule has a mouth initially covered by a lid; when the spores inside the capsule are mature, the lid falls off and the spores are released, to be dispersed by wind. (Compare SPHAGNUM and ANDREAEIDAE.) In liverworts the capsule is usually ovoid or spherical and has no lid. On ripening, the capsule usually splits into four ‘valves’, which open out to release the spores.
3. A dry fruit, normally dehiscent.
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capsule