Phylum - BRYOPHYTA

Mosses can be found just about everywhere ( that ia on land) from the Artic to the Antarctic and most definetely including the Tropics.
There are aproximately 8,000 species of mosses worldwide, a little less than a third of them in Tropical America

The taller mosses may have a very elaborate conducting area analogous to the xilem and phloem that we find in the more advanced plants.Mosses with a well developed conductive system can be as tall as 80 cm. ( or for the metric impaired, approximately 32 inches high!

In the true  Mosses the sporophyte ( the 2N stage which produces the spores and looks like a stem with a capsule on top) is the most complex relative to the other 2 groups of bryophytes. Unlike the liverworts, it grows out of the gametophyte very early in development and completes its growth protected by a tissue derived from the base (venter) of the female organ, the calyptra.

• The sporophyte is partly photosynthetic.
• In mosses unlike hepatics, the capsule has a columella of sterile tissue and carries only spores.
• At the tip of the capsule can be seen a cap or operculum, separated from the main body of the capsule by a ring. This lid will eventually detach from the capsule, releasing the spores.

Alhtough a number of Classes exist in the phyla, we just introduce two here... the ones you are most likely to see about....

Class - Sphagnopsida (Peat Mosses or Sphagnum

This group of mosses is associated with bogs found throughout the world... not only in the colder moister areas up north ( think of the canadian and irish peat bogs) but also down south, as in Georgia where they are responsible for forming the great Okeefenokee Swamp

They have an incredible moisture ( and unfortunately for other plants nutrient) -holding ability as they produce large porous cells which can trap water even when dead.. The are known to hold up to 40x their weight in water.
They also produce acidic compounds which prevent microbial growth... an important consideration if you can hold that much water. Thus, areas with a lot of peat growth are resistant to bacterial and even more important fungal attack.
Mats of these resistant peat mosses can accumulate over thousands of years. Eventually hardy microbes which can live in the anerobic conditions of the lower submerged layers produce gas which causes 'chunks of these mats' to rsie up creating the 'floating islands' like you see in the Okeefenokee ( indian for floating land) or the New Jersey Pine Barrens. Over time tree and bush seeds will germinate here and eventually form a forest underlain with peat and water.

Class -Bryopsida ("True" Mosses):

Have you hiked through a forest and noticed bright green patches of low lying plants carpenting the banks of the creeks. If so, you probably sighted a colony of mosses. Although these ancients have been around for a long time they can still compete with their more advanced relatives under the right conditions: moist and rather shady. The tight packed formations are critical to their survival... given they don't have true roots they must form a mass which can funnel in rian, and hold on to moisture and create a rather humid mini system of their own.

	Spore release in many mosses is aided by the movement of "teeth" - known as peristome teeth - which are arranged radially around the mouth of the capsule, and revealed when the operculum is detached.     The peristome shown below contributes to the dispersal of spores a function that in hepatics is helped by the presence of elaters.
	Bryum photograph by Sean Edwards

  

Life cycles and features of the Bryophytes	The mosses	The liverworts
The hornworts	Economic and ecological roles of the bryophytes	Differences between the mosses and liverworts
	Return to introductory Bryophyte page