Difference between revisions of "How to Examine a Plant"

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|title=How to Examine a Plant
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|keywords=Rainforest, Rain forest, how to identify, plants, leaves, tool,, routine, study a plant
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|description=This page provides a systematic way of examining a plant specimen in order to determine its identity to the family, genus, or even species level.
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When you come across a new plant in the forest, how do you go about studying and identifying it?  The following routine provides a systematic way of examining a plant specimen in order to determine its identity to the family, genus, or even species level.  Follow “the routine” in conjunction with the [[Key to Plant Families]], the [[Jimenez Matrix]],  or other botanical key to identify your specimen.  If you think you know what family a plant belongs to, you can also jump to the appropriate plant family page.  All you need for starting material is a branch and some leaves.
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When you come across a new plant in the forest, how do you go about studying and identifying it?  The following routine provides a systematic way of examining a plant specimen in order to determine its identity to the family, genus, or even species level.  Follow “the routine” in conjunction with the [[Key to Plant Families]], [[The Matrix]],  or other botanical key to identify your specimen.  If you think you know what family a plant belongs to, you can also jump to the appropriate plant family page.  All you need for starting material is a branch and some leaves.
  
Is your specimen a '''monocot''' or '''dicot'''?  Monocots have parallel leaf venation and usually have strap-like leaves.  Some, like palms and aroids, have large leaves with pinnate venation, but the secondary veins are parallel.  Dicots have veins that fan out in various netted patterns and are usually broad-leaved.
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Is your specimen a '''[[Glossary|monocot]]''' or '''[[Gloassary|dicot]]'''?  Monocots have parallel leaf venation and usually have strap-like leaves.  Some, like palms and aroids, have large leaves with pinnate venation, but the secondary veins are parallel.  Dicots have veins that fan out in various netted patterns and are usually broad-leaved.
  
How are the leaves arranged along the stem ('''phyllotaxy''')?  Are they '''alternate'''? '''Opposite'''? Or are there 3 or more leaves at a node arranged in a '''whorl'''? Alternate leaves may be '''distichous''', coming off the stem in two ranks in a well-defined left-right-left-right pattern.  In other cases alternate leaves may be '''spirally''' arranged.  Opposite-leaved plants are often '''decussate''', meaning that one pair of opposite leaves is offset by 90° from the next pair of leaves.
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How are the leaves arranged along the stem ('''[[Glossary#LEAF ARRANGEMENT|phyllotaxy]]''')?  Are they '''[[Glossary#LEAF ARRANGEMENT|alternate]]'''? '''[[Glossary#LEAF ARRANGEMENT|Opposite]]'''? Or are there 3 or more leaves at a node arranged in a '''[[Glossary#LEAF ARRANGEMENT|whorl]]'''? Alternate leaves may be '''[[Glossary#LEAF ARRANGEMENT| distichous]]''', coming off the stem in two ranks in a well-defined left-right-left-right pattern.  In other cases alternate leaves may be '''[[Glossary#LEAF ARRANGEMENT| spirally]]''' arranged.  Opposite-leaved plants are often '''[[Glossary#LEAF ARRANGEMENT| decussate]]''', meaning that one pair of opposite leaves is offset by 90° from the next pair of leaves.
  
Are leaves '''simple''' or '''compound'''?
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Are leaves '''[[Glossary#LEAVES|simple]]''' or '''[[Glossary#LEAVES|compund]]'''?
*If compound are they '''pinnate''' (feathery with multiple leaflets coming off of an elongated continuation of the petiole known as a '''rachis''') or '''palmate''' (hand-like with leaflets radiating from a single point)? (note that the “stem” of a leaflet is called the '''petiolule''')
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*If compound are they '''[[Glossary#LEAVES|pinnate]]''' (feathery with multiple leaflets coming off of an elongated continuation of the petiole known as a '''rachis''') or '''[[Glossary#LEAVES|palmate]]''' (hand-like with leaflets radiating from a single point)? (note that the “stem” of a leaflet is called the '''[[Glossary#LEAVES|petiolule]]''')
 
*If pinnate, are they mono- or bi-pinnate? (in bipinnate leaves, the leaflets themselves are pinnate)
 
*If pinnate, are they mono- or bi-pinnate? (in bipinnate leaves, the leaflets themselves are pinnate)
*If mono-pinnate, do they have an even number of leaflets occurring in pairs along the rachis ('''paripinnate''')?  Or do they have an odd number of leaflets with a terminal leaflet at the end of the rachis ('''imparipinnate''')?
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*If mono-pinnate, do they have an even number of leaflets occurring in pairs along the rachis ('''[[Glossary#LEAVES|paripinnate]]''')?  Or do they have an odd number of leaflets with a terminal leaflet at the end of the rachis ('''[[Glossary#LEAVES|imparipinnate]]''')?
 
*If palmately compound, how many leaflets do they have?
 
*If palmately compound, how many leaflets do they have?
  
Are the margins of the leaves or leaflets '''entire''' (smooth) or '''serrate''' (toothed)? (Note that serrate leaves are not particularly common in the tropics.)
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Are the margins of the leaves or leaflets '''[[Glossary#LEAVES|entire]]''' (smooth) or '''[[Glossary#LEAVES|serrate]]''' (toothed)? (Note that serrate leaves are not particularly common in the tropics.)
  
Are '''stipules''' present or absent?  For some reason, much of tropical botany seems to hinge on these seemingly insignificant flaps of tissue, or the scars that they leave behind. Use a hand lens!  Some are '''terminal''', meaning they are located at the tip of a branch.  Most are located where the petiole meets the stem.  They are usually tiny and usually fall off by the time the leaf has matured.  The only evidence of their presence may be a tiny scar.
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[[Image:Monstera.jpg|thumb|right|400px|''Monstera'' species of family Araceae]]
  
Do cut stems or severed petioles yield '''exudations'''?  Are the exudations clear and watery? Milky white?  Yellow, orange, or red? Do exudations flow freely or do they need to be squeezed from the petiole?  
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Are '''[[Glossary#MISCELLANEOUS TRAITS OF LEAVES AND STEMS|stipules]]''' present or absentFor some reason, much of tropical botany seems to hinge on these seemingly insignificant flaps of tissue, or the scars that they leave behind.  Use a hand lens! Some are '''[[Glossary#MISCELLANEOUS TRAITS OF LEAVES AND STEMS|terminal]]''', meaning they are located at the tip of a branch.  Most are located where the petiole meets the stem.  They are usually tiny and usually fall off by the time the leaf has matured. The only evidence of their presence may be a tiny scar.
  
Do crushed petioles exude slightly sticky '''mucilage'''? Chew up a petiole and then feel between thumb and forefinger while looking for sticky strands as you spread your fingers apart. (Don’t make the mistake of chewing on a leaf that clearly has milky white or colored latex, as it’s likely to be highly toxic! There is a real, but subtle, difference between mucilage and latex exudations.)
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Do cut stems or severed petioles yield '''[[Glossary#MISCELLANEOUS TRAITS OF LEAVES AND STEMS|exudations]]'''?  Are the exudations clear and watery? Milky white?  Yellow, orange, or red?  Do exudations flow freely or do they need to be squeezed from the petiole?  
  
Is there an '''odor'''? Crush up the leaves and smell themOr tear off a leaf and immediately smell the broken petiole. What kind of odor do you detect?  Primitive “ranalean odor”, anise, turpentine, unripe avocado, guava, eucalyptus, rank, sweet, green bean, or just plain nasty?  Or like crushed leaves?
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Do crushed petioles exude slightly sticky '''[[Glossary#MISCELLANEOUS TRAITS OF LEAVES AND STEMS|mucilage]]'''? Chew up a petiole and then feel between thumb and forefinger while looking for sticky strands as you spread your fingers apart(Don’t make the mistake of chewing on a leaf that clearly has milky white or colored latex, as it’s likely to be highly toxic! There is a real, but subtle, difference between mucilage and latex exudations.)
  
Examine the upper and lower surfaces of the leaf carefully with a hand lens (an essential piece of field equipment).  Experiment by holding the leaf up to the light.  Are translucent dots, also called '''pellucid dots''', visibleAre the pellucid spots only in the shape of round dots or are some shaped like dashesAre pellucid dots larger at the margin of the leaf or uniform in sizeLeaves with pellucid dots often have an odor as well.
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Is there an '''[[Glossary#MISCELLANEOUS TRAITS OF LEAVES AND STEMS|odor]]'''?  Crush up the leaves and smell them.  Or tear off a leaf and immediately smell the broken petiole.  What kind of odor do you detectPrimitive “ranalean odor”, anise, turpentine, unripe avocado, guava, eucalyptus, rank, sweet, green bean, or just plain nastyOr like crushed leaves?
  
Can you peel the bark? Does it peel in long strings, sometimes referred to as “'''strong bark'''or “'''stringy bark'''”?
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Examine the upper and lower surfaces of the leaf carefully with a hand lens (an essential piece of field equipment).  Experiment by holding the leaf up to the light. Are translucent dots, also called '''[[Glossary#MISCELLANEOUS TRAITS OF LEAVES AND STEMS|pellucid dots]]''', visible?  Are the pellucid spots only in the shape of round dots or are some shaped like dashes?  Are pellucid dots larger at the margin of the leaf or uniform in size? Leaves with pellucid dots often have an odor as well.
  
Are '''hairs''' presentUse a hand lens to determine if they are present and if they are star shaped ('''stellate''') or T-shaped (as in [[Malpighiaceae]]) or some other shape?  Are they white or brown?
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Can you peel the barkDoes it peel in long strings, sometimes referred to as “'''[[Glossary#MISCELLANEOUS TRAITS OF LEAVES AND STEMS|strong bark]]'''or “'''[[Glossary#MISCELLANEOUS TRAITS OF LEAVES AND STEMS|stringy bark]]'''”?
  
How are the primary, secondary, and tertiary '''veins''' arranged?   
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Are '''[[Glossary#MISCELLANEOUS TRAITS OF LEAVES AND STEMS|hairs]]''' present?  Use a hand lens to determine if they are present and if they are star shaped ('''[[Glossary#MISCELLANEOUS TRAITS OF LEAVES AND STEMS|stellate]]''') or T-shaped (as in [[Malpighiaceae]]) or some other shapeAre they white or brown?
  
This routine for studying a plant was developed by Dr. Humberto Jimenez.  If you can answer most of the questions, then you should be able to determine the family of your plant specimen using Susan Letcher’s [[Key to Plant Families]], the [[Jimenez Matrix]], or the key in Alwyn Gentry’s “A Field Guide to the Families and Genera of Woody Plants of Northwest South America”.
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How are the primary, secondary, and tertiary '''[[Glossary#VEINS|veins]]''' arranged? 
  
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This routine for studying a plant was developed by Dr. Humberto Jimenez-Saa.  If you can answer most of the questions, then you should be able to determine the family of your plant specimen using Susan Letcher’s [[Key to Plant Families]], [[The Matrix]] developed by Dr. Humberto Jimenez-Saa, or the key in Alwyn Gentry’s “A Field Guide to the Families and Genera of Woody Plants of Northwest South America”.
  
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Latest revision as of 02:12, 26 January 2015

How to Examine a PlantPlant Family ListKey to Plant FamiliesTop Ten ListsThe MatrixNavigation Bar.jpg
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When you come across a new plant in the forest, how do you go about studying and identifying it? The following routine provides a systematic way of examining a plant specimen in order to determine its identity to the family, genus, or even species level. Follow “the routine” in conjunction with the Key to Plant Families, The Matrix, or other botanical key to identify your specimen. If you think you know what family a plant belongs to, you can also jump to the appropriate plant family page. All you need for starting material is a branch and some leaves.

Is your specimen a monocot or dicot? Monocots have parallel leaf venation and usually have strap-like leaves. Some, like palms and aroids, have large leaves with pinnate venation, but the secondary veins are parallel. Dicots have veins that fan out in various netted patterns and are usually broad-leaved.

How are the leaves arranged along the stem (phyllotaxy)? Are they alternate? Opposite? Or are there 3 or more leaves at a node arranged in a whorl? Alternate leaves may be distichous, coming off the stem in two ranks in a well-defined left-right-left-right pattern. In other cases alternate leaves may be spirally arranged. Opposite-leaved plants are often decussate, meaning that one pair of opposite leaves is offset by 90° from the next pair of leaves.

Are leaves simple or compund?

  • If compound are they pinnate (feathery with multiple leaflets coming off of an elongated continuation of the petiole known as a rachis) or palmate (hand-like with leaflets radiating from a single point)? (note that the “stem” of a leaflet is called the petiolule)
  • If pinnate, are they mono- or bi-pinnate? (in bipinnate leaves, the leaflets themselves are pinnate)
  • If mono-pinnate, do they have an even number of leaflets occurring in pairs along the rachis (paripinnate)? Or do they have an odd number of leaflets with a terminal leaflet at the end of the rachis (imparipinnate)?
  • If palmately compound, how many leaflets do they have?

Are the margins of the leaves or leaflets entire (smooth) or serrate (toothed)? (Note that serrate leaves are not particularly common in the tropics.)

Monstera species of family Araceae

Are stipules present or absent? For some reason, much of tropical botany seems to hinge on these seemingly insignificant flaps of tissue, or the scars that they leave behind. Use a hand lens! Some are terminal, meaning they are located at the tip of a branch. Most are located where the petiole meets the stem. They are usually tiny and usually fall off by the time the leaf has matured. The only evidence of their presence may be a tiny scar.

Do cut stems or severed petioles yield exudations? Are the exudations clear and watery? Milky white? Yellow, orange, or red? Do exudations flow freely or do they need to be squeezed from the petiole?

Do crushed petioles exude slightly sticky mucilage? Chew up a petiole and then feel between thumb and forefinger while looking for sticky strands as you spread your fingers apart. (Don’t make the mistake of chewing on a leaf that clearly has milky white or colored latex, as it’s likely to be highly toxic! There is a real, but subtle, difference between mucilage and latex exudations.)

Is there an odor? Crush up the leaves and smell them. Or tear off a leaf and immediately smell the broken petiole. What kind of odor do you detect? Primitive “ranalean odor”, anise, turpentine, unripe avocado, guava, eucalyptus, rank, sweet, green bean, or just plain nasty? Or like crushed leaves?

Examine the upper and lower surfaces of the leaf carefully with a hand lens (an essential piece of field equipment). Experiment by holding the leaf up to the light. Are translucent dots, also called pellucid dots, visible? Are the pellucid spots only in the shape of round dots or are some shaped like dashes? Are pellucid dots larger at the margin of the leaf or uniform in size? Leaves with pellucid dots often have an odor as well.

Can you peel the bark? Does it peel in long strings, sometimes referred to as “strong bark” or “stringy bark”?

Are hairs present? Use a hand lens to determine if they are present and if they are star shaped (stellate) or T-shaped (as in Malpighiaceae) or some other shape? Are they white or brown?

How are the primary, secondary, and tertiary veins arranged?

This routine for studying a plant was developed by Dr. Humberto Jimenez-Saa. If you can answer most of the questions, then you should be able to determine the family of your plant specimen using Susan Letcher’s Key to Plant Families, The Matrix developed by Dr. Humberto Jimenez-Saa, or the key in Alwyn Gentry’s “A Field Guide to the Families and Genera of Woody Plants of Northwest South America”.


Return to Main Page
How to Examine a PlantPlant Family ListKey to Plant FamiliesTop Ten ListsThe MatrixNavigation Bar.jpg