Steps to take in Description of Plants through Leaf examination
(Note: the following
terms have been drawn from different sources
and occasionally different
terminology has been found for similar phenomena.
You may not be able to identify your plant conclusively through these steps, but you can narrow
down the possibilities by eliminating a number of choices.)
terminology has been found for similar phenomena.
You may not be able to identify your plant conclusively through these steps, but you can narrow
down the possibilities by eliminating a number of choices.)
First, it is important to understand the Leaf Structure
Next, answer the following six questions:
1. What shape is
the Leaf Blade?
2. How are the leaves grouped on the stem?
3. How are the leaves positioned on the stem?
4. What form do the Leaf Veins take?
5. What does the edge or Margin of the Leaf look like?
6. What does the Leaf Base look like?
2. How are the leaves grouped on the stem?
3. How are the leaves positioned on the stem?
4. What form do the Leaf Veins take?
5. What does the edge or Margin of the Leaf look like?
6. What does the Leaf Base look like?
1. What Shape is the Leaf Blade?
- Linear - i.e.
narrow, with
almost parallel sides
- Lanceolate - longer than broad and tapering to a point at the tip
lanceolate leaf
- Oblong - much longer than wide, with nearly parallel sides
- Elliptic - shaped like an ellipse, wider at the center and tapering to equal tips
Elliptic / Oblong shaped leaf - unknown tree
- Ovate - egg-shaped, broader at the base than the tip
- Cordate - heart-shaped, either the leaf shape or base
Heart - or cordate - shaped leaf
- Reniform - kidney-shaped
- Spatulate - shaped like a spatula or spoon
- Orbicular - round
Orbicular
shaped leaf with palmate veins - from the conestegia oerstediana or "lengua de vaca" tree
Illustration from Missouri Botanical Garden
2. How are the leaves grouped on the stem?
Leaf Groupings
a) Simple - leaves appear aloneb) Compound - leaves grow in groups, and are made up of leaflets
- Palmate (e.g.
cecropia)
- leaflets form a fan shape
- Pinnate (e.g. cedro dulce) - leaflets are opposite each other on the stem
- Bipinnate - leaflets are in pairs of pinnate groups (also referred to as double pinnate or twice pinnate)
- Trifoliate - three-divided
- Ternate - three times three divided
trifoliate example
Pinnate leaf of the cedro dulce (cedrela tonduzii)
3. How are the leaves positioned
on the stem?
Leaf Position
a) Opposite - directly opposite each otherb) Alternate - on both sides, but one above the other
c) Whorled - growing out from the stem all at the same height
d) Basal - the leaves grow out from the bottom of the plant's stem, near the ground
4. What form do the
Leaf Veins take?
a) Palmate - radiating
out
from a central spot at the base of the leaf (like the palm of a hand)b) Pinnate - the vein runs the length of the blade and the secondary veins branch off on either side of the main central vein (like a feather)
(see above for illustrations)
6. What does the edge or Margin of the Leaf look like?
Leaf Margins
1. Entire - no indentations or extrusions (see leaf structure at top for illustration)2. Toothed margins (leaf has serrations or indentations on its edges):
a) Toothed - small pointed extrusions ?
b) Dentate - larger points pointing outward
c) Serrate - pointing towards the apex
d) Crenate - rounded
e) Incised - deeply cut, with sharp, irregular teeth
Toothed leaf
3. Lobed margins
a) Lobed - deep indents or sinuses
b) Sinuate - very wavy margin
c) Undulate - wavy margin
Illustration
from Missouri Botanical Garden
7. What does the
Leaf Base look like?
a) Truncate - the base
is
flattenedb) Oblique - one side begins
higher up the petiole than the other:
Oblique leaf of the elm