Online Curriculum - Identification (Unit 4)

aspen leaf
Basic morphology of an aspen leaf.

Leaves are good indicators of climatic conditions in terrestrial environments. Their shape and the patterns that their veins and edges form provide important information about the environment in which they lived. Let's take a moment to familiarize ourselves with leaf identification. You can also download a printable PDF version of each of these identification guide pages to help you complete the exercise.

Basic Leaf Terminology

  • Lamina - the expanded, flat part of a leaf or leaflet.
  • Apex - usually the upper ~25% of the lamina.
  • Base - usually the lower ~25% of the lamina.
  • Margin - the edge of the lamina.
  • Petitole - the stalk of the leaf.
  • Primary vein - the widest vein of the leaf and any others of like width and/or course.
  • Secondary veins - the next widest class of veins after the primary, originating from the primary or primaries.
  • Tertiary veins - the next widest class of veins after the secondary or primary veins, originating from the secondaries.
  • Higher order veins - the narrowest class of veins after the tertiary veins, originating from any vein.

Click here to see an enlargement of the tertiary and higher order veins.

Leaf Symmetry

leaf symmetry

Leaf Shapes

leaf shapes

Margin Types

leaf margins
Margin Tooth Terminology

Tooth Terminology

  • Sinus - the space between teeth
  • Apical side - the side of the tooth towards the apex of the leaf
  • Tooth apex - the apex of the tooth on the margin
  • Basal side - the side of the tooth towards the base of the leaf

Vein Types

Last updated: March 20, 2016

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