Why Does Moss Only Grow on One Side of a Tree?

David W. Kramer kramer.8 at OSU.EDU
Mon Oct 21 08:35:49 EST 1996

>I'm in grade 3 and my teacher asked me to find out about why moss only
>grows on one side of a tree. My parents already surfed the web and found
>some bryology sites, but they were too complicated.
>I'd appreciate any references that answer this question. Thx.

Good morning, Robyn!

One of the most exciting things about science is that it gives us an
opportunity to THINK about all the possible answers to a question.  We call
this "forming a hypothesis."  Then, our next step is to go to  reference
books, our professional colleagues and more recently the Internet to
discover what people already know about the subject before we launch into a
time-consuming discovery activity on our own.  I don't think your teacher
wanted you to merely find someone else's answer to the question.  At least
I hope your teacher wanted you to discover how science works... how one
would find the answer to such a question using the methods of science.  So,
let me suggest that you will enjoy this assignment much more if you follow
these steps:

1.  Go to the woods (or your backyard, playground... anywhere there are
trees) to find out if the statement really is true.  DOES moss really grow
only on one side of trees?  If it grows on all sides, does it seem to grow
BETTER on one side?  Which side?  Is there anything different about the
tree on one side or another?  Is there anything different about the
environment on one side or another?  [Before you do this you might want to
look in an encyclopedia or science book to make sure you understand what a
moss is... and the way you might be able to tell the difference between a
moss, an alga, and a lichen.]
2.  Now THINK about what you have observed and develop a list of possible
explanations.  Choose the explanation which seems to be the least
complicated.  This is your HYPOTHESIS.  This is what you would test by
experiment or by more detailed observations if you were to actually perform
the scientific research.  [Before, during, or immediately after this step
you will want to go to the library to find out what others have discovered
about what mosses need for their survival or what they need to grow best.]
3.  Design a list of activities you could perform to "prove" that your
hypothesis is right or wrong.  Then, perform as many of these activities as
you can.  Write down all of your thoughts, plans, experimental steps, data
tabulation charts, observations, etc. in a "journal" (just a few pages in
your notebook!).  You might even take some photos or make some drawings to
document your findings.
4.  Analyze your data.  That is, try to determine whether the information
you gathered is sufficient to answer the question.  Do you need to take
additional steps?  Did you look at enough trees?  Did you look at different
species of trees (oak, beech, maple, elm, ash, etc.)?  Does the type of
tree make a difference?  Did you look at trees in different locations (full
sun, deep shade in the forest, etc.)?  People often use the word "moss" to
include mosses, algae, and lichens.  Do each of these behave differently in
regard to where they grow on the tree trunks?
5.  Tell others what you have discovered.  This is the "publication" step
of scientific inquiry.  You can 1) write a report for your teacher, 2) with
your teacher's permission, give an oral report of your findings to your
classmates, 3) post your findings on the Internet (I hope you'll send me
your results by e-mail), etc.

You will notice that I didn't answer your question!!!  Science isn't just
about answers its about the method of anwering questions.  If I were to
give you the answer, you'd miss all the fun of finding out for yourself!
Good luck!  And by the way........  I hope you seriously consider a career
in science, especially in Plant Biology.  We need all the best minds we can
find to help us answer questions about the interesting life of plants.  You
might enjoy reading David Attenborough's book, "The Private Life of Plants"
or look in your library or video rental store for the videotapes of a TV
documentary he made with the same title.  It's amazing!

Dr. David W. Kramer
Department of Plant Biology
Ohio State University at Mansfield
1680 University Drive
Mansfield, OH  44906
(419) 755-4344  FAX:  (419) 755-4367
e-mail:  kramer.8 at osu.edu

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