I.  Leaf Anatomy

	A.  Structure
		1. Blade - flat portion of a leaf
		2. Petiole - holds the leaf to the stem
		3. Stipules – leaf-like outgrowths at the base of the petiole
	4. Trichomes – hair-like structures on leaves
		5. Stomates - openings which allow for gas exchange necessary for
 			Photosynthesis.
		6. Guard cells – specialized structures that open and close the stomates

	B.  Types of leaves (see page 130 for examples)
		1..  simple leaf - single, undivided blade
		 	a.  example - maple leaf

		2.  compound leaf - a blade divided into many leaflets
			a..  pinnately compound –  leaflets do not all originate from one point
				1. example - walnut
			b..  palmately compound – all leaflets attach centrally to the end of petiole
				1.  example - buckeye
			c.  succulent - adapted leaves that serve as a reservoir for water
				1.  Examples: Aloe, cactus,  and some plants that look like stones

3.  Arrangement of Leaves on Stem
a.  alternate – only one leaf attaches at each node
b.  opposite – two leaves grow from each node
c.  whorled – three or more leaves grow at each node

4. Leaf Venation
a.  parallel – primary veins run parallel to each other
b.  netted – resembles a net
1. palmately netted – major veins radiate out from one point
2. pinnately netted – major veins branch off along main vein
  
5.  Abscission -  The normal falling of leaves or other plant parts
a.  caused by physiological changes in the plant

II.	Leaf Adaptations

	A.  Conifers
		1.  Speical group of trees that have needle or scale-like leaves covered in a
waxy layer.
		2..  Includes: pines, spruce, firs, redwoods, and cedars
a.  Most specimens are evergreen (do not shed their leaves during winter)
	B.  Deciduous – plants which lose their leaves during specific seasons
		1.  Deciduous leaves often change color and then abscise (fall off)

	C.  Circadian Rhythms – biological rhythms that follow a 24 hr. cycle
		1.  Example – stomates opening and closing

	D.  Transpiration – loss of water vapor due to evaporation
1.  Guttation – Excess water droplets forced from leaves
			a.  Usually occurs at night when transpiration can’t occur due to closed
stomates.

		2..  Wilting – reaction from plants to reduce surface area and thus slow water
	loss from transpiration.

III.  Modified Leaf Structures

	A.  Spines – modified leave for protection
		1.  often found on desert cacti

	B.  Tendrils – specialized leaves that form on vines
		1.  helpful for clinging and climbing up structures

	C.  Bud Scales – modified leaves designed to protect delicate meristem at the bud

	D.  Bulb – a short modified stem surrounded by fleshy leaves.
		1. Examples: tulips, daffodils, lilies, onions (alliums)

	E.  Epiphyte – a plant that grows attached to another larger plant that it uses for
 support

	F.  Insectivorous Plants – modified leaves designed to trap insects to supplement
	the plants nutritional needs.