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The Pedicel or Seta

The seta has undoubtedly been developed for the purpose of raising the spore-case to a height where the spores may be most advantageously scattered. In many mosses the seta becomes abruptly larger just below the spore-case to form an apophysis. This may be long and cylindrical, or of many other forms. In the Polytrichum mosses it is a more or less flattened disk.

The seta is surrounded at the base by a sheath which is the vaginule and may be the remains of the base of the archegonium.

The pedicels (setae) have various methods of twisting or turning while growing so as to bring the developing spore-case into positions most favourable with reference to light and moisture.