Life cycle of Polytrichum

Polytrichum sp

Alternation of generation is clear in the life of Polytrichum sp.,it starts from spores haploid develop into protonema.The haploid protonema grow into male and female gametophytes.Male and female gametophytes , with antheridia and archegonia respectively are found in the different plants.

Antheridium produes antherozoids while archegonium produces oospheres.Antherozoid swims through a film of moisture to an archegonium and fertilizes the oosphere.The diploid zygote develops into a sporophyte.The sporophyte grows a long stalk or seta,that emerges from the archegonium.

Attached by its foot,the sporophyte remains nutritionally dependent on the gametophyte.Meiosis occurs and haploid spores develop in the sporangium of the sporophyte.When sporangium lids pop,the spores released.

 

Images sources : Google