The zygote or oospore is the unit of sporophytic generation in Moss plant. Soon after fertilization the zygote enlarges and occupies the entire veuter cavity of archegonium. This now divides by transverse division into epibasal and hypobasal cells. Two apical cells with two cutting faces is formed at each end of young embryo as a result of further division in epibasal and hypobasal cell. Upper epibasal half divides and forms capsule and some portion of seta while lower hypobasal of half forms the rest portion of seta and foot. The surrounding tissue of oospore derived from gametophyte forms the calyptra. The capsule tissue is latter differentiated into central endothecium and peripheral amphitecium.
The endothecuim for further divisions is differentiated into central sterile collumela and outer fertile archegonium. The cells of archegonium transform into spore mother cells which later undergoes reduction division forming haploid spores. Amphitecium gives rise to outer wall of the spore sac and wall layers of capsule. Amphithecium in upper region of capsule forms five concentric rings of cells. The cells of first ring from inner peristonial layer and other peristonial layer develops from the second ring operculum is formed from third and fourth rings. Fifth rings form the epidermis. The endothelial cells in the lower epidermis region form conducting region. The amphitherium in the lower region forms spongy chlorenchymatous tissue and epidermis which possesses stomata. Epidermal cells at the base of operculum enlarge radially and form annulus. The seta cells elongate and form elongated seta while foot cells form short and bulbous foot.
Thus the sporophyte of Funaria is highly advanced. It is differentiated into a foot embedded in the tissue of female shoot, a thin long seta and a bear shaped capsule.
The mature capsule when seen in longitudinal section consist of a cap like operculum at top. Below operculum peristome with peristomial teeth are present.
There is present a well developed central collumela surrounded by a spore sac, near which air spaces are present wall of capsule is multilayered. Lower part of capsule or apophysis has conducting stand and epidermis of this region possesses the stomata.
Dispersal of spores:
In dry conditions the cells of annulus shrink, operculum sheds off, peristomial teeth open and spores are liberated out. These spores are carried to long distances by wind to germinate in favourable conditions.
The Gametophyte: The spore is the unit of gametophyte. Each spore is a uni-nucleate structure covered with two layered wall the exine and intine. The spore on germination forms green filamentous protonema which develops several buds which give rise to new moss plant.
Alternation of generation in Funaria (Moss): It is the change in life cycle from gametophyte to sporophyte generation and from sporophyte to gametophyte generation. Funaria (Moss) plant is itself gametophyte which gives rise to sporophyte generation. Gametophyte generation produces gametes and sporophyte generation produces spores. Male and female gametes fuse and give rise to a diploid zygote which functions as mother cell of sporophyte phase. Sporangium is a simple structure completely dependent upon the gametophyte. The haploid spores on germination give rise to gametophyte. Alternation of generation takes place by the genetic union which results in the formation diploid zygote which on germination always develops into a sporangium which produces haploid spores which function as mother cells of the gametophytic phase.