This document provides information about leaf characteristics that can be used to identify tree species. It discusses leaf arrangements, types, margins, textures, and shapes. The external structures of leaves such as the blade, petiole, margin, and veins are defined. Internally, leaves have epidermal layers, mesophyll tissue including palisade and spongy layers, stomata, veins, and trichomes. Coniferous trees are identified by their needle-like evergreen leaves and reproduction via cones, while deciduous trees have broad, flat leaves that fall off annually and reproduce via flowers. A few exceptions to the general coniferous and deciduous classifications are also noted.

1. LEAVES

2. Leaf
Characteristics/
ID

3. Leaf Characteristics-Deciduous
1. Leaf arrangement: whorl, alternate,
opposite
2. Leaf type: simple or compound
3. Leaf margin: entire, lobed, toothed–
others exist
4. Leaf texture: hairy, waxy, rough, smooth,
thick, thin, etc.
5. Leaf shape: ovate, obovate, lanceolate,
cordate, elliptical, etc. – others exist

4. 1.

5. What is the leaf arrangement?

6. What is the leaf arrangement?

7. 2. Leaf Type

8. Simple Compound
• Only one leaf blade
• Joined by its stalk to the
woody stem
• Examples: maple, oak,
aspen, beech
• Made up of several
leaflets
• Leaflets are joined to a
midrib that is not
woody
• Examples: ash, walnut,
sumac

9. Simple or Compound?

10. What is the leaf type?

11. 3. Leaf Margins
1. Entire = margin lacks teeth (smooth)
2. Serrate = saw-tooth with the teeth pointing
forward
3. Lobe = projecting part or segment of the leaf
- Space between two lobes is a sinus
- Example maple or oak

13. 4. Leaf Texture
hairy, waxy, rough, smooth, thick, thin, etc.
Describe the “leaf” of the aloe plant

14. 5. Leaf Shapes
• Ovate = egg-like shape, broadest part below
the middle
• Obovate = shaped like an egg, broadest part
above the middle
• Lanceolate = much longer than wide
• Cordate = shaped like a heart
• Elliptical = have an ellipse shape, broadest
part in the middle

16. External Leaf
Structure

17. External Leaf Structure
Tip
Margin
Vein
Spine
Midrib
Base
Blade
Petiole

18. External Leaf Parts
1. The large broad part of a leaf is the leaf
blade
 Large surface area for photosynthesis
 Supported by a system of veins that contain xylem
and phloem
2. Main vein running down the middle is the
midrib
 Help position the blade in a way that it is facing a
light source

19. External Leaf Parts
3. The leaf blade is connected to the stem by
the petiole
 Lifeline between the leaf and the rest of the plant
 Water and minerals flow into the leaf blade and
food flows out of the leaf blade through the
petiole
4. The edge of the leaf blade is referred to as
the margin
 Wavy, toothed, lobed, and entire or smooth.

20. 5. On top of the leaf is a waxy non-cellular
layer called the cuticle
 Prevents water from escaping
 Plants in bright arid conditions have thick cuticles to
retain water
6. Veins
 Contain xylem and phloem (stem cells that
allow for movement of nutrients/waste)
External Leaf Parts

22. Internal Leaf
Structure

23. Internal Leaf Parts
1. The epidermis is the skin-like layer of cells on the
top AND the bottom surface of the leaf
– The epidermis may be one or many layers thick
– Protective
2. Between the epidermal layers is the mesophyll
– Photosynthetic occurs in mesophyll cells
– Network of veins containing xylem and phloem tissues
– 2 Types:
• Palisade mesophyll – tightly packed cells standing on end
directly beneath upper epidermis
• Spongy mesophyll – loosely packed cells, form air spaces to
hold products of photosynthesis, under palisade

24. What are the functions of the internal
components of a leaf?
3. Leaves have openings in the
epidermis called stomata
- singular: stoma
- Allow the diffusion of carbon
dioxide, oxygen, and water.
- Specialized cells called guard
cells control the opening and
closing of the stomata

25. 4. Trichomes
- Specialized cells that appear as hairs on the
leaves of some plants
- Reduce water loss by slowing air movement
- Discourage some pests from devouring the
leaves
- Example: soybeans

28. Cuticle
Epidermis
Palisade
Chloroplast
Spongy
Layer
Xylem
Phloem
Epidermis
Guard Cell
Stoma
Cuticle
Vein
Air Space

29. Additional Comments –
Internal Structure
• Chloroplast
– Organism containing chlorophyll which is green and collects
light energy
• Xylem
– Transports water and nutrients up the plant
• Phloem
– Transports sugars down the plant
• Guard Cell
– Controls moisture and gas exchange
– Open when plant is well watered and closed when the plant
is dry

30. Coniferous VS
Deciduous

31. Which is Which?

32. Characteristics of Conifers
• Needle shaped leaves
• Seeds that develop
inside cones
• Evergreen – green
year round
• Gymnosperm, conifer,
softwood
• Examples: pine,
spruce, hemlock, fir

33. Examples of conifers
Balsam fir
Douglas fir
Fraser fir Scotch pine
Red pine
White pine

34. Conifer leaves
• Needle like • Scale like

35. Conifer needles
• Clusters • Singles

36. Deciduous Tree Characteristics
• Broad flat leaves
• Lose all leaves each
year in the fall
• Angiosperm
(flowering plants),
broadleaf, hardwood
• Examples: oak,
maple, beech, aspen,
ash

37. Deciduous examples
Red oak Red maple
Black locust
White
birch
Crimson king
Honey locust
beech
Elm

38. Exceptions
• Larch trees have cones and needles, but lose
their leaves each year.
• Yew trees have needle shaped leaves and are
evergreen but have berries not cones.
• Holly trees have broad flat leaves and it is
evergreen.