Background info on Physco biology and culture

Physcomitrella patens is a monoecious moss, which requires simple growth conditions for the completion of its life cycle. Moss gametophytes exist in two morphologically distinct forms: the juvenile filamentous tissue called protonema and the adult leafy tissue called gametophore. However, the molecular mechanism for the transition from the juvenile (protonema) to the adult (gametophore) stage is not precisely known.

Here is a good site that show the Physco Lifecycle and various structures.

gametophore

This is a gametophore, with non-vascular leaflets (source Wikimedia commons).

gametophore (PO:0030018) A shoot system that consists of the shoot axes and non-vascular leaves of a plant in the gametophytic phase.

protonema

protonema (PO:0030003):

A portion of chlorenchyma tissue that develops directly from a spore and grows by division of an apical cell to form filaments that are one cell wide and dicotomously branching.

Useful references:

Prigge, M. J. and Bezanilla, M. (2010). Evolutionary crossroads in developmental biology: Physcomitrella patens. Development, 137, 3535 -3543. (link)