MOSSES

Mosses are a botanical division (phylum) of small, soft plants that are typically 1–10 cm tall, though some species are much larger, like Dawsonia, the tallest moss in the world which can grow to 50 cm in height. They commonly grow close together in clumps or mats in damp or shady locations. They do not have flowers or seeds, and their simple leaves cover the thin wiry stems. At certain times mosses produce spore capsules which may appear as beak-like capsules borne aloft on thin stalks.

There are approximately 12,000 species of moss classified as Bryophyta. Bryophyte remains a collective term to include not only mosses, but also liverworts and hornworts (although taxonomy is under review). They differ from other plants in that they have no true vessels for the transport of water and nutrients.

Mosses have a complex life cycle in which sexual and asexual stages alternate. The familiar green leafy structures produce male and female organs at their tips and, similar to the situation in animals, the male sperm swim in order to reach and fertilize and female cell on another plant. For this reason, mosses are always found in humid environments. Without rain or dew for the sperm to swim in, fertilization cannot occur.

From the fertilized gamete, a filament grows up with a spore-bearing capsule at its tip (sporophyte). It usually takes about a quarter to half a year for the sporophyte to mature. Within the capsule, the minute spores mature (chromosome number is halved again). They are released, carried on the air like dust particles and, if they find a suitable environment to germinate, the process can begin again.

Source: Wikipedia