Why do mosses grow close together

Looking through them will give you a good introduction to moss diversity. The following references are very useful for more detail about this great diversity, from the macroscopic view to the microscopic level. Much of the following information on this page has come from these books.

While it may be true to say that a moss gametophyte has "stems and leaves", that statement leaves a lot unsaid. Ptychomnium aciculare , showing stems. Moss stems are generally fairly weak and, if free-standing, fairly short. Stem colour varies from green to shades of brown, for example, Ptychomnium aciculare. Stems are often green when young, with chlorophyll in the cells. The mosses in the families Dawsoniaceae and Polytrichaceae provide striking exceptions to the general rule stated at the beginning of the previous paragraph.

Within these families the stems are fairly firm, with the plants being upright and quite robust. In this photo of a Dawsonia you can see the brown stems quite clearly. Polytrichum or Dawsonia plants can be quite tall, with the free-standing stems of some species growing to over 60 centimetres in height.

Hence it is not surprising that people often mistake these mosses for herbaceous flowering plants. Though the stems in the Dawsoniaceae and Polytrichaceae are fairly firm, they contain no lignin and are not woody.

There are essentially two growth forms for moss plants. In one the stems are basically erect, with just one upright stem per plant or with the initial erect stem producing some branches, depending on the species , giving the individual plant a tufty or shrubby appearance. In the other growth form the moss will have mostly trailing stems. If the stems cling to the substrate the overall appearance, to the naked eye, will be of a creeping plant but in some species they hang, almost curtain-like, from branches.

The trailing mosses are typically highly branched with the branches growing along the substrate - but many such species also produce short, upright branches. Branches develop from surface cells in the originating stem and in most mosses branches are simple, single outgrowths from the originating stems.

In Sphagnum you will see branches developing in fascicles. Within such a fascicle, some of the branches will be stout and spreading, while others are slender and drooping. In species with an upright growth form the stems may be very short almost non-existent to quite long - as already noted for some Dawsonia species. If there is only a very rudimentary stem the plant will look like a bunch of leaves growing from just a single point. In genera like Polytrichum and Dawsonia the individual plants are typically just single stems, with branching rare.

Amongst the upright mosses there are the so-called "dendroid" mosses, which have a spread of branches atop a vertical stem. The word " dendroid " means "tree-like" and it's easy to see how apt that term is.

In some cases, instead of branches in all directions, there'll be a fan-like spread of branches. You'll also see such mosses called "umbrella mosses" - an equally apt descriptive expression. There are many erect-stemmed species of moss where the plants grow very closely together in mat-like or cushion-like colonies. You can see a somewhat cobblestone-like surface. If you take a very small sample from the colony and look at it side-on you see this.

As I walked down the muddy paths today, enjoying the rare January sunshine, I noticed that many of the trees near Little Huckleberry Creek had bright green moss growing on the south side of the trunks. Since it rained recently, and the sun is out, the green chlorophyll went into action to generate some food for the moss while the conditions are just right! Next Next post: Winter Survival.

The narrow, pipe-like sporophyte is the defining characteristic of the group. The sporophytes emerge from the parent gametophyte and continue to grow throughout the life of the plant. Stomata appear in the hornworts and are abundant on the sporophyte. Photosynthetic cells in the thallus contain a single chloroplast.

Meristem cells at the base of the plant keep dividing and adding to its height. Many hornworts establish symbiotic relationships with cyanobacteria that fix nitrogen from the environment. Hornworts : Unlike liverworts, hornworts grow a tall and slender sporophyte.

The life cycle of hornworts also follows the general pattern of alternation of generations and has a similar life cycle to liverworts.

The gametophytes grow as flat thalli on the soil with embedded gametangia. Flagellated sperm swim to the archegonia and fertilize eggs. However, unlike liverworts, the zygote develops into a long and slender sporophyte that eventually splits open, releasing spores. Additionally, thin cells called pseudoelaters surround the spores and help propel them further in the environment. Unlike the elaters observed in liverworts, the hornwort pseudoelaters are single-celled structures.

The haploid spores germinate and produce the next generation of gametophytes. Like liverworts, some hornworts may also produce asexually through fragmentation. Life Cycle of Hornworts : The life cycle of hornworts is similar to that of liverworts. Both follow the pattern of alternation of generations.

However, liverworts develop a small sporophyte, whereas hornworts develop a long, slender sporophyte. Liverworts also disperse their spores with the help of elaters, while hornworts utilize pseudoelaters to aid in spore dispersal. Mosses are bryophytes that live in many environments and are characterized by their short flat leaves, root-like rhizoids, and peristomes. More than 10, species of mosses have been cataloged.

Their habitats vary from the tundra, where they are the main vegetation, to the understory of tropical forests. Mosses slow down erosion, store moisture and soil nutrients, and provide shelter for small animals as well as food for larger herbivores, such as the musk ox. Mosses are very sensitive to air pollution and are used to monitor air quality.

They are also sensitive to copper salts. Such salts are a common ingredient of compounds marketed to eliminate mosses from lawns. Mosses form diminutive gametophytes, which are the dominant phase of the life cycle.

Green, flat structures resembling true leaves, but lacking vascular tissue are attached in a spiral to a central stalk or seta. The plants absorb water and nutrients directly through these leaf-like structures.

The seta plural, setae contains tubular cells that transfer nutrients from the base of the sporophyte the foot to the sporangium. Some mosses have small branches. Some primitive traits of green algae, such as flagellated sperm, are still present in mosses that are dependent on water for reproduction. Other features of mosses are adaptations to dry land. One variety, Anoectangium compactum, can survive an incredible 19 years without water [source: Richardson ]!

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