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What Does Peat Moss Look Like?

If you look closely at peat moss (Sphagnum spp.), you can see structures that resemble stems, branches, and leaves of flowering plants. You will find no roots, however, because mosses lack internal systems for fluid transportation. Peat mosses can be easily recognized by their characteristic heads, which are approximately between a quarter and half an inch in diameter.
 
 

  Single sphagnum
Sphagnum angustifolium
The Head (Capitulum)
 
The Sphagnum head mirrors the specific growth pattern of peat moss. Branches bud and develop around the apical cell at the center of the head. Because no stem elongation takes place at this stage, all origins of developing branches are located on the same horizontal plane. Thus, the head of Sphagnum is a cluster of branches of various ages, with the youngest at the center and the most mature at the periphery. Some species spread long peripheral branches that give the head an Edelweiss resemblance.
 
 
  Sphagnum head
Sphagnum angustifolium
 
    Stem and Branches
 
Sphagnum branches
Sphagnum quinquefarium
 
  In most higher plants, the growth of a stem or trunk preceds the development of branches. In peat moss, stem elongation takes place between fully developed branches at the periphery of the head.
   The branches grow in bundles (fascicles), with their close proximity providing capillary spaces that can hold and conduct water. Some of the branches are spread out, anchoring the individual plant in the moss cluster, others droop along the stem. Between the stem surface and these pendent branches, water is conducted similar to a wick soaking up liquid wax.

 
 
  Horizontal bar
 
 
  Try an Experiment
 
 
  (1) If you have access to non-protected peat moss, collect about 2 handful of it.
(2) Dry it for at least 1 week at room temperature.
(3) Weigh the dry moss.
(4) Submerge in water, soak it for several minutes, and let it drip off.
(5) Weigh the wet moss.

Peat moss can absorb and retain so much water that its weight should have increased about twentyfold.
 

 
  Horizontal bar
 
 
The Leaves
 
All peat mosses are foliose. Stems and branches bear different types of leaves that vary in shape among the various species. Stem leaves may be erected, spreading or drooping, some, e.g., those of Sphagnum fimbriatum, have wide bases and fringed edges. While stem leaves are distributed sparsely, never touching each other, branch leaves grow in dense rows and often overlap each other like shingles. The narrow spaces between branches and leaf bases can hold water. This external water storage by branch leaves can sometimes even be observed through a ten-fold magnifying glass.
 
 
  Sphagnum leaves
Branch leaves of
Sphagnum magellanicum

 
Cell network of leaves
 
  Cell Network
 
Sphagnum leaves have a characteristic single-layer cell net that distinguishes them from other mosses. At 40fold magnification, the microscope shows long, photosynthetic chlorocytes alternating with the much larger hyalocytes. Hyalocytes are fully differentiated, dead cells that store water. Spiral fibers fortify their cell walls, and protect them from collapse. Large pores facilitate the entrance of water and allow even algae and unicellular animals to enter theses cells and live inside them. Hyalocytes contribute substantially to the turgid appearance of peat moss.

 
 
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