1. Leaves
By: Becky McGuire

2.   Function
make food used by plants for growth & reproduction

3. Parts Dicots a. blade: broad, thin part of leaf
b.  petiole: thin stem attaching leaf to stem
1. sessile: leaves with no petiole
c.   midrib: large, central vein
d.  margin: edge of leaf

4. Parts Dicots, continued
E.  secondary vein: branches from main vein
F. tip: top of leaf
G.  base: bottom of leaf

5. Diagram of a Dicot Leaf Tip Midrib Blade Petiole Base Margin Secondary
Vein
Midrib
Blade
Petiole
Base
Margin

6. Monocots a. sheath: portion of leaf blade surrounding stem
b.  ligule: “collar” extension of sheath curving around stem
auricles: appendages that surround stem at junction of blade and sheath

7. Diagram of a Monocot Leaf
Stem
Ligule
Auricles
Sheath

8. WHERE WILL YOU EVER USE THIS?
For identification of weeds and plants for fertilizer, pesticides, etc.

9. Leaf Characteristics Simple
a.   one blade per leaf
ex: grass, oak, apple

10. Compound
a.   several leaflets
ex: sumac, locust

11. identification
shape, margin, tip, base (see handouts)

12. venation: arrangement of veins in a leaf
1.  parallel: extend from base to tip of leaf in parallel lines
ex. Grasses/monocots
2.  dichotomous: forked veins, begin at base and go out from central point to tips
ex. Ferns, ginko
3.  pinnate: secondary veins extend from midrib
ex. Poplar
4.  palmate: principal veins extend from petiole
ex. Maple, sweetgum

13. arrangement on stem
1.  alternate: leaves occur at alternate spots on stem; single leaf at each node
a.   oak, beech
2.  opposite: leaves occur two at a node on opposite sides of stem
a.   maple, ash, dogwood (MAD; only 3)
3. whorled: 3 or more leaves at each node