Sphagnum erect, leafy, branched gametophyte with chlorophyllose cells and hyaline cells. This stage dominates the environment where "Sphagnum" grows, obliterating and burying the protonema and eventually building up into layers of dead moss called peat. Carpets of living "Sphagnum" may be attacked by various fungi, and one fungus that is also a mushroom, "Sphagnurus paluster", produces conspicuous dead patches. When this fungus and other agarics attack the protonema, "Sphagnum" is induced to produce nonphotosynthetic gemmae that can survive the fungal attack and months later germinate to produce new protonema and leafy gametophytes. It is unknown whether the leafy stage can produce
Plant cell quite elongated, and may divide transversely to give a septate appearance. The role of this cell type is to support the plant in axes still growing in length, and to confer flexibility and tensile strength on tissues. The primary wall lacks lignin that would make it tough and rigid, so this cell type provides what could be called plastic support – support that can hold a young stem or petiole into the air, but in cells that can be stretched as the cells around them elongate. Stretchable support (without elastic snap-back) is a good way to describe what collenchyma does.