Plant Morphology

...must have concise mental pictures of leaf, bud, stem, flower and fruit morphlology. 

Leaf Morphology

The postion of the bud determines whether the leaf is simple or compound.

Leaf Morphology

If the bud is located in the axil (angle) of a single leaf and the stem, therefore, the leaf is single.

Leaf Morphology

If the bud is located in the axil (angle) of a leaf structure with more than one leaf, therefore, the leaf is termed compound.

Other Types of Compound Leaves

Palmately Compound: in this situation each leaflet is

attached to a common point.

Odd Pinnate: A compound pinnate type of leaf with an odd number of leaflets.

Even Pinnate: A compound pinnate type of leaf with an even number of leaflets.

Leaf Morphology Angiosperms Leaf Type

Bipinnately Compound:  are twice divided. What was considered the leaflet of the pinnately compound leaf is now another leaf-bearing axis to which additonal leaflets are attached (leaflets on each side of the other leaflet).

Gymnosperm Leaf Types

Cone-bearing or naked seeded plants often display different leaf types than those associated with angiosperms.  Not all conifers (or cone-bearers) have evergreen foilage (exceptions include Taxodium, Metasequoia, Larix, and Pseudolarix).

Gymnosperms Leaf Types

Awl-like:  The needles (leaves) are shaped like an awl.  They are usually very sharp to touch. Many Juniperus (Junipers) exhibit awl-shaped foilage.  This character is manifested in juvenile forms of juniper, however, there are many species and cultivars which possess the awl-like or needle foilage in youth and old age.

Gymnosperms Leaf Types

Scale-like:  Scale-like foilage overlaps like the shingles on a roof or the scales of a fish.This type of foilage is relatively soft to the touch.

Gymnosperm Leaf Types

Needle-like:  Needle-like foilage is typical of several evergreen genera and species.  The drawing depicts the foilage of a 5 needled pine.  In the genus pinus the leaves (needles) are usually contained in fascicles of 2,3,2, and 3,or 5.  Other species such as Abies, Picea, Cedrus, Pseudotsuga, and Taxus, have the needles borne singly or in clusters along the stem.  The needles may be relatively flat (2-sided) or angular (often quadrangular) in cross-section.

Arrangement of Leaves

Many vegetative keys employ the arrangement of leaves and buds as a basis for seperation.  The use of the four categories by the student allows her to categorize plants into groups and assists in eliminating many plants from consideration in the process of positive identification.

Arrangement of Leaves

1 of 4

1.) Opposite:  Leaves and buds directly across from each other on the stem.

Arrangement of Leaves

2 of 4

2.) Alternate:  Leaves and buds are spaced in alternating fashion along the axis of the stem and seldom, if ever, are seated directly across from each other.

Arrangement of Leaves

3 of 4

3.) Subopposite:  Subopposite refers to a condition where the leaves and buds are not spaced sufficiently far apart to be considered alternate nor are they perfectly opposite, hence, the term subopposite.

Arrnagement of Leaves

4 of 4

4.) Whorled:  Whorled refers to a condition when three buds and leaves (or more) are present at a node. 

Types of Venation

Pinnate.  The leaf has a prominent central vein

(often termed the midrib) which extends from the base, where the petiole attaches to the blade, to the apex of the leaf.  If the interveinal areas were removed the overall effect would be that of a fishbone.  Pinnate venation occurs in the leaves of many plant types.  The elm (Ulmus) and oak (Quercus) are classic examples. 

Types of Venation

Palmate. There are several main veins all of approximately equal size which extend from the base of the leaf to the apex of the lobe or margin of leaf.

Types of Venation

Dichotomous. A very limited type of venation, the most familar representative of which is Ginkgo biloba.  The basal veins extend for a distance and then branch forming a "Y" type pattern.

Types of Venation

Parallel.  Typical of many monocotyledonous plants.  The veins run essentially parallel to each other along the long axis of the leaf.

Leaf Shapes

1. Ovate
2. Lanceolate
3. Cordate
4. Ellipitcal
5. Spatulate
6. Obovate
7. Oblanceolate
8. Obcordate
9. Oblong
10. Linear
11. Peltate
12. Cuneate
13. Reniform
14. Hastate

Leaf Bases

1. Cuneate
2. Acute
3. Rounded
4. Cordate
5. Oblique
6. Sagittate
7. Hastate
8. Truncate
Auriculate

Leaf Margins

1. Entire
2. Serrate
3. Serrulate
4. Doubly Serrate
5. Dentate
6. Crenate
7. Incised
8. Sinuate
9. Undulate
10. Lobed

Leaf Apices

1. Acuminate
2. Acute
3. Obtuse
4. Truncate
5. Emarginate
6. Obcordate
7. Mucronate
8. Cuspidate

Stem and Bud Morphology

Deciduous woody plant identification in winter must be based on stem, bud, and bark characteristics.  Buds and stems offer the principle means of identification.