Please define me secondary protonima?

Please define me secondary protonima ? ( When it is produced and from where )

Protonema in mosses, part of the gametophyte that develops from the spores (primary protonema) or from the rhizoids, stems, and leaves (secondary protonema). The protonemata of leafy mosses are shaped like ramose green threads; those of liverworts and sphagnum mosses are poorly developed and platelike. Buds arise on the protonemata and develop into leafy shoots that bear antheridia and archegonia (gametophores). The protonema usually dies shortly after its development, but sometimes (for example, in the moss Buxbaumia) it remains throughout the plant’s entire life.