Study Leaves: Lesson 2 - How does a leaf function?

Tilia leaf

      With  regard  to  the  distribution  of  the  strands  which  traverse  the  green blades  we  distinguish  between  blades  with  a  single  main  strand  and  blades with  several.  Blades  with  a  single  main  strand  are  distinguished  as  feather-like  (pinnate)  and  radiating.  In  the  former  the  lateral  strands  rise  successively  from  the'  main  strand  or  midrib  at  almost  equal  intervals,  and  they take,  at  first  at  least,  a  parallel  course.  In  radiating  leaves  the  later  strands spring  directly  from  the  main  strand  at  the  base  of  the  blade  and  run  like rays  towards  its  edge.  Leaf  blades  with  several  main  strands  are  not nearly  so  varied  in  form  and  structure  as  those  with  only  one,  as  a  rule  they are  long-shaped  with  unbroken  margin,  and  the  most  remarkable  variations among  them  are  in  the  number  of  strands,  their  thickness  and  their  direction.

• This is the second lesson; the first lesson about leaf vocabulary and identification is here.

Require for Observation: Sample clip art drawings for teachers to share with students below. Teachers should also have a few real leafs to show the class the: veins, stalk, stem and tips. 

Method of Student Observation:

• A  suitable  leaf  should  be  tom  in order  to  show  the  tough  and  fibrous character  of  the  veins,  and  the  softer nature  of  the  intermediate  parts  of the  leaf. The arrangement  of  the  veins should  next  be  studied,  holding  the leaf  up  to  the  light  and  looking through  it,  when  necessary,  to  render the  smaller  veins  visible. Finally,  the  leaves  should  be  classified  according  to  their  venation.
• As  much  as  possible  of  this  information  should  be  obtained  from the  class.
• A  plant  may  often  be  killed  by cutting  off  all  its  leaves.  Why  is this?
  

How to Grade Study Notes For Student Journals: Every student will need a journal to write in weekly for this online nature study series. Teacher will assign the weekly content in advance.

• Make sure the facts are: written in complete sentences, the first word of each sentence capitalized, and a period should be included at the end of each sentence.
• Spell check your vocabulary and write the words correctly.
• Dress up your journal entries with student clip art, drawings of your own in color or in black and white.
• Student may also include photographs of their own taking for extra credit.

Look for the following facts about leaf anatomy inside of student journals. Assign a point value to the quality of the content.

• The  veins  (like  the  stalk  and  the midrib)  contain  fibers,  and  are,  therefore,  tough; while  the  other  portions of  the  leaf  are  soft  and  cellular.  The  fibres  are  the  vessels  by  which the  sap  circulates. The  veins  generally  form  a  network,  but  sometimes  they  are  parallel.
• Uses  of  Leaves for The Plant - Leaves  are  the  breathing  organs of  the  plant. They  take  in  gaseous  plantfood  from  the  atmosphere. Leaves have  microscopic  holes  ( stomata )  to  enable them  to  perform  these  functions.) 
• In  the  leaves,  the  sap  of  the plant  is  exposed  to  light  and air.  This  causes  the  formation  of  starch,  sugar,  gum,  and other  substances  required  by the  plant.
• To humans many leaves  are  used  as  food (cabbage,  lettuce,  cress),  some for  making  beverages  (tea), and  many  for  the  preparation of  drugs.
  

Video at Youtube for Students to Watch:

1. Structure of the leaf by FuseSchool
2. Venation of leaf by 7activestudio
3. Travel Deep Inside a Leaf by California Academy of Sciences

Draw the anatomy of a leaf and label it's parts. There is clip art below given as the teachers diagram examples. Students should either bring a leaf from home to draw and label it's parts or gather a leaf from the school playground on a walk with his or her classmates to do the same with. After drawing their own example of the leaf they may color it in with pencils or crayons.

Review What should be illustrate by the students:

• The stalk joins the leaf to the stem of the plant.
• The little branch-looking lines on the leaf are called veins.
• The stalk joins the leaf to the stem of the plant and runs up the middle of the leaf to the tip.
• There are two kinds of leaves called simple and compound. Identify the type you will draw.

Free Student Clip Art: Clip art may be printed from a home computer, a classroom computer or from a computer at a library and/or a local printing service provider. This may be done from multiple locations as needed because our education blog is online and available to the general public.

Illustration of midrib, stalk, blade for the Lime tree.
Illustration of Leaf of Wallflower and Leaf of Rose.

Illustrated lily leaf with veins running side by side.
Illustrated lime leaf with a network of veins.
Illustrated small piece of leaf much enlarged showing
cells and breathing holes.