Twigs

Lab Work

This lab is the follow up to the field trip you had for the lab assignment for tissues.  Twigs are "stems" from trees.  Identify the winter twigs below.  The quiz will be identifying twigs, fruits, and conifers giving common name. Genus species for the images of twigs presented.

Grading Rubric:

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Twig identification

In this lab you will apply the information you learned in the field lab week five to identifying specimens in the lab.  You will be presented with 10 winter twigs and 5 conifers that you will need to identify.  You will be able to use the dicotomous key found from 213 to 218 in your lab book and you will identify genus and specie of each twig.  Also, you may find the interactive key at http://www.cnr.vt.edu/dendro/dendrology/syllabus/twigkey/key1.htm useful.  Note that if you have access to it, you can use any good Field Guide to Trees and Shrubs such as the Peterson Field Guide Series form Houhton Mifflin Publishing Co.   In your lab book, look at pages 213 to 216 to see the Key to Deciduous Trees in their winter condition (woody twigs) and then 216 to 218 to see the key for conifers.  Note that the key is a dicotomous (2 parts) key giving information for identifying specific deciduous (part 1) or conifer (part 2) we are seeking to identify.  Note that sometimes you will be able to identify the Genus, but will not be able to narrow it down to the specific specie.  In that case you give the Genus, and list spp. which means specific specie unknown.

At the end of this lab the successful student will be able to

• Identify the structures found on a woody twig
• Recognize visible fruits on winter twigs
• Differentiate conifer Genus by leaf, needle arrangement
• List of the answers to identification questions

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Identify the structures found on a woody twig

In your reading of chapter 6, you learned the structures that are used to identify twigs:

Use this terminology as well as the field trip information in this lab.

Upon entering the lab, the student finds the lab table with twigs laid out for the lab.  

Here is an example of what is done in the lab.  A student has identified twig 4 from the table and made the appropriate entry into his lab notebook.   Note the  top line shows common and scientific name (Genus specie).  Note the next two lines list the characteristics of the twig that the student used on the dicotomous key to identify the winter twig (page 214 toward the bottom) and that below that the student makes a diagram of the twig.  When you do this lab, you should do the same thing in YOUR lab notebook, except that you will need to use the image of the twig where the students in this lab actually had twigs that they could handle.

For the rest of this lab, we will show you the twig and help you identify the characteristics you will use to apply the key.  Then you should try to identify the Genus and specie by using your dicotomous key and checking the twig in the next objective to see if you have identified it correctly.  (Did you notice that the Genus is always started with a capital letter and the specie is always lower case?)

1. and in a student's notebook:   Note the characteristics: 
   • branching is alternate  (that means that the leaf scar will also be alternate)
   • Terminal bud is absent
   • Note:  You would have to look with a magnifying glass at the actual twig to see this, but there are lenticels forming horizontal lines and several scales covering each bud.
   • catkins
2.   and in a student's notebook:  Note the characteristics:
   • branching is alternate  (that means that the leaf scar will also be alternate)
   • Terminal bud is absent
   • A single scale covering winter bud (Axillary bud completely surrounded by leaf scar.)
   • Achene (Fruit ball) 
3.   and in a student's notebook:    Note the characteristics:
   • Branching is alternate
   • Terminal bud absent
   • Extremely long, thin (implies drooping) branchlets
   • Yellowish color
   • NOTE:  You will have to use the supplement to look up this one.  It is not in you lab book.
4.   and in a student's notebook:    Note the characteristics:
   • Branching is opposite
   • Terminal bud is larger than axillary bud
5.   Note the characteristics:
   • Branching is alternate
   • Terminal bud absent
   • Stipualar spines present
6.     Note the characteristics:
   • Branching is alternate
   • twigs and buds are hairy
   • fruits are red, long, and hairy.
7.     Note the characteristics:
   • Branching is alternate
   • Terminal bud present
   • lenticels present (little white specks form horizontal lines)
8.      and in a student's notebook   Note the characteristics:
   • Branching is alternate
   • Terminal bud is present
   • Leaf appears pointed on edges. 
9.       Note the characteristics:
   • Terminal bud is present
   • Pith is chambered. 
   • Leaves, when visible are pinnately compound
   • Compare its chambered pith to the continuous pith on your other specimen
10.           Note the characteristics:
    • Terminal bud is present
    • Pith is continuous
    • Twigs green and aromatic when bruised (root beer aroma)
    • Leaves appear single bi, or tri-lobed (May appear as Michigan Mit)
    • Compare its continuous pith to the chambered pith on your other specimen

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Recognize visible fruits on winter twigs

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Differentiate conifer Genus by leaf, needle arrangement

Here is a table with the conifer twigs for the students to identify  

1.   Note the characteristics:
   • long singular needles that arise singularly from the stem
   • note needles often appear "blunt" and "flat" on ends of the fir trees
   • (216, 7a)
2.     Note the characteristics:
   • (217 10b)
   • leaves arise singularly from branch and 4 angled and sharp on ends
3.    Note the characteristics:
   • leaves narrow and flattened (1 to 5 centimeters)
   • fruit berry like (aril)
4.     Note the characteristics:
   • (Not in key... look for this one on the fieldtrip information) 
   • Leaves are needle-like in clusters of two
   • Needles are long, about 15 centimeters
5.   Note the characteristics:
   • Needles arise in clumps of two are are short (7.5 centimeters)
   • Bark appears butterscotch in color)
6.   Note the characteristics:
   • Needles appear in clumps of five and are 7 to 12 centimeters long.
   • soft and flowing.  Note this is the Michigan state tree.

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List of the answers to identification questions

-- birch. Betula spp. --
-- black walnut. Juglans nigra --
-- cherry. Prunus spp. --
-- concolor fir. Abies concolor --
-- eastern white pine. Pinus strobus --
-- locust. Gleditsia spp. --
-- maple. Acer spp. --
-- red pine. Pinus resinosa --
-- red oak. Quercus rubra --
-- sassafras. Sassafras spp. --
-- scots pine. Pinus sylvestris --
-- spruce. Picea spp. --
-- sumac. Rhus typhyna --
-- sycamore. Platanus spp. --
-- weeping willow. Salix babylonica --
-- yew. Taxus canadensis

Here are the answers to the twigs above.  I will supply the common name.  You must know the scientific name as well as the common name for your quiz.

1. White Birch   2. Sycamore   3.Weeping willow    4.Maple     5.Locust    6.Sumac   7.Cherry    8.Red Oak      9.Black Walnut        10. Sassafras

Here are the answers to the Conifers

1. Concolor fir       2. Blue Spruce      3. Yew       4. Red Pine       5.Eastern White Pine

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