Marvelous Mosses

I visited the Dunwoody Nature Center last week and found an assortment of species of mosses.

Probably breaking off from green algae sometime during the Permian Period 299 to 251 million years ago, moss is a non-vascular plant, meaning, unlike trees, shrubs, vines and wildflowers, moss does not have tubes made of xylem to transport water from the roots to the leaves. Moss has rhizomes instead of roots and typically one central stem with leaves arranged around it. Each stem, which is often covered with infinitesimal leavesm is known as a gametophyte. The gametophyte contains both the female and male parts of the plant, which create spores.

Worldwide, mosses can grow any where from 0.5 mm to 50 cm tall. Its habitat can vary, but moss is usually found in wet, shady areas on rocks, trees or directly on the ground. Some moss can be found at the bottom of streams, on rocks under waterfalls, or at the bottom of lakes. The leaves are also specialized to pull moisture out of the air or water that flows over it. Most mosses are green, but some are black or red.

Mosses are part of the division Bryophyta. They are further subdivided into three groups: granite mosses, which has 100 species of mostly black mosses that grow in alpine and arctic areas; peat mosses, which comprises about 350 light green and red species and grows in bogs and is the main component of peat; true mosses, which comprises about 14,000 species and are the typical mosses seen in the Piedmont area in Georgia.

Because mosses are non-vascular, they must live in damp areas. Some species have a way of bringing water from the rhizomes to the leaves. They accomplish this feat using a concept known as capillary action. The rhizoids cannot carry water like roots, but many species wrap their rhizoids together in bundles to create small spaces that cause water to defy gravity. The adhesion forces between the water and rhizomes pull the first molecule of water upwards and the intermolecular forces between the molecules helps that molecule drag the others along with it until the mass of water reaches a height where gravity counteracts its movement. This physical concept can be found in other areas like when water creeps up the bristles of a paintbrush or through a paper towel. The water finds the stem and makes its way to the leaves through cells or around them. In the leaves, the water then contributes to photosynthesis.

Due to extremely minute differences between species, I am unable to identify mosses that I come across. Here are some pictures of the species I found at the Nature Center:

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