AHCPCM201A Recognise
Plants
Plant Structure notes
LEAVES
These notes are a guide only and should be used in
conjunction with information provided by your teacher.
© NSW TAFE Commission
These notes have been compiled by printWest, using
student notes from the Open Training and Education
Network (OTEN), TAFE teachers and other TAFE Commission
sources.
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Table of Contents
Plant morphology..................................................................................................................................... 4
Types of leaves ......................................................................................................................................... 6
Leaf shapes............................................................................................................................................. 11
Shapes of compound leaves .................................................................................................................. 11
Shapes of simple leaves ......................................................................................................................... 16
Shapes of leaf margins ........................................................................................................................... 26
Shapes of leaf apices .............................................................................................................................. 30
Shapes of leaf bases ............................................................................................................................... 33
Other morphological features of leaves ................................................................................................ 37
Leaf attachments ................................................................................................................................... 40
Phyllotaxy or Leaf arrangement............................................................................................................. 42
Leaf surfaces .......................................................................................................................................... 50
Appendix ................................................................................................................................................ 54
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Plant morphology
What is plant morphology?
Plant morphology is the study of those external features of plants used for recognition
and classification. In the study of plant morphology we are concentrating on the
members of Class Angiospermae, so we can say that a typical flowering plant is
composed of:
•
a shoot system consisting of stems, leaves, flowers, fruit and seeds;
•
a root system.
Main function of the plant organs
The main functions of the various plant organs are listed in Table 2 and Figure 8 shows
the basic organs of a 'typical' flowering plant and their main functions.
Table 2: Main functions of the five plant organs of a typical flowering plant
Organ
Function
roots




anchoring plants in the soil
absorbing water and nutrients from the soil
storage of some food substances
a means of vegetative propagation
stems


supporting leaves, flowers and fruits
providing a pathway for movement of
substances between the roots and the leaves
(translocation)
storage of food substances
photosynthesis within herbaceous stems
a means of vegetative propagation



leaves





flowers
fruit

manufacture of food substances by the
process of photosynthesis for use by all parts
of the plant
evaporation of water from leaf surface
(transpiration) allowing more water to enter
the roots
exchange of the gases, carbon dioxide and
oxygen, between plant and atmosphere
storage of food substances
a means of vegetative propagation aesthetic
value

production of seed as a result of pollination
and fertilisation
aesthetic value


protection of seed
help in dispersal of seeds
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Figure 8: Main function of the plant organs of a 'typical'
flowering plant
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Types of leaves
Simple leaves
Simple leaves are characterised by having a single leaf blade
(or lamina) which is supported by a system of veins. A
typical simple leaf of a dicotyledon can be seen in Figure 1.
Figure 1: A typical simple leaf
Before we consider what some of the labels on this simple
leaf mean, go out into your garden and collect some leaves
attached to small sections of stem. If you don't have a
garden, use leaves from a potted plant to locate these
morphological features.
Now that you have some leaves in front of you, locate the
following parts.
• Lamina: this is the blade of the leaf. The shape of the
lamina is used more than any other feature in plant
identification and recognition.
• Petiole: this is the leaf stalk, which attaches the lamina
to the stem. The auxiliary (or lateral) bud is found in the
axil of the petiole and stem. If the petiole is absent and
the base of the lamina is attached directly to the stem,
the leaf is said to be sessile (ie without a petiole).
• Leaf base: this term refers to the shape of the lower
third of the leaf.
• Leaf apex: this term refers to the shape of the upper
third of the leaf.
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• Leaf margin: this term refers to the way in which the
edge of the lamina is indented or shaped.
• Main vein or midrib: this is the central main vein of a
leaf with reticulate venation.
• Lateral veins: these are the veins which radiate from the
main vein and form a network in a reticulate leaf.
• Auxiliary bud: this is not actually part of the leaf, but
the location of this bud is important in recognising the
difference between simple and compound leaves. It will
always be found above the petiole (or leaf base if the leaf
is sessile) on the stem, in the axil of the leaf and the
stem.
Compound leaves
Compound leaves are thought to have evolved from simple
leaves. As the world's surface dried out, many species with
large simple leaves were faced with the problem of severe
desiccation (drying out) due to the large surface area of
their lamina. In response to the drier environment, the
lamina reduced to the area around the main vein and the
larger lateral veins, thus reducing the overall transpiration
surface. This is shown in Figure 2.
Figure 2: The evolution of compound leaves showing the
reduction in the lamina to the area around the main lateral
veins.
Let us now label the parts of a compound leaf. You should
venture out into the garden again to see if you can find a
few compound leaves on which to locate these specific
morphological features.
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Figure 3: A typical compound leaf.
Notice the position of the auxiliary bud. It is still located in
the axil of the petiole and stem, but now the lamina has
concentrated around the lateral veins. These smaller 'leaves'
are correctly called leaflets. These structures are also
sometimes called pinnae, but I prefer to keep this term for
use in describing the leaflets of ferns, when the term 'leaflet'
is never used and pinna is used exclusively.
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If there is a leaflet at the apex of the structure, it is referred to as a terminal leaflet.
The petiole is still the stalk which attaches the base of the leaf lamina to the stem. The stalk
of a leaflet is called a petiolule.
The rachis is the main axis of a compound leaf extending from the petiole to the end of the
leaflets-the 'stalk' to which the leaflets are attached. It is equivalent to the main vein in the
simple leaf.
Stipules
These are leaf-like or scale-like structures found at the base of the petiole in some plants.
They are appendages of the leaf or petiole and may be found on both simple and compound
leaves. Two variations are shown in Figure 4.
Stipules may carry out photosynthesis, protect the auxiliary bud or be modified to assist in
supporting the plant-for example, as tendrils or spines.
The presence or absence of stipules is often an important feature for plant identification.
Many Pelargonium species have stipules, as do Rosa species. Have a hunt around your
garden for plants with stipules.
Figure 4: The position of a stipule on a rose (left) and a sweetpea.
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 Self Assessment 1
Write down the answers to the following questions. When you have finished, check them
against the answers provided at the end of this unit. If you have made any mistakes, revise
the relevant study notes in this unit. Label the following diagrams of a simple leaf and a
compound leaf.
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Leaf shapes
One of the most important aids in plant identification is the shape of the lamina in a simple
leaf and the arrangement of the leaflets in a compound leaf.
We are going to look at the arrangement of the leaflets in compound leaves before looking
at the shapes of simple leaves.
With compound leaves the arrangement of the leaflets is usually the only characteristic that
we need to study. Sometimes we may need to look at the specific characteristics of each
leaflet, but this does not happen very often.
Shapes of compound leaves
Pinnate
This term describes a compound leaf which has a row of leaflets on each side of the rachis.
There are two types of pinnate leaves, paripinnate and imparipinnate.
Paripinnate
These compound leaves have an even number of leaflets which are usually in pairs along
the rachis. Example: Toona australis.
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Imparipinnate
These leaves have an uneven number of leaflets due to the presence of a terminal leaflet.
Example: Rosa species and Fraxinus species.
Bipinnate
These leaves are pinnately divided twice. Example: Jacaranda mimosifolia, Acacia baileyana.
Tripinnate
This term describes leaves pinnately divided three times. Example: Nandina domestica.
Trifoliolate
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These leaves have three leaflets. Example: Cissus species, Ceratopetalum gummiferum.
Palmate (digitate)
These leaves have several leaflets (more than three and up to any number) emanating from
one point. Example: Schlefflera actinophylla (umbrella tree).
{£n Self Assessment 2
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 Self Assessment 2
Write down the answers to the following questions. When you have finished, check them
against the answers provided at the end of this unit. If you have made any mistakes, revise
the relevant study notes in this unit.
Name the shape of each of the following compound leaves:
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 Self Assessment 2
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Shapes of simple leaves
The following terms can be used to describe
a leaf shape (the shape of the lamina) and
thus to avoid having to use long descriptions
in plant identification.
Acicular
This term describes a needle-shaped leaf. The
cross section can be circular, triangular or many
sided. Example: Pinus species.
Linear
A linear leaf is long and narrow with sides parallel
(about ten times as long as broad). The crosssection is a narrow rectangle. Example: Banksia
ericifolia.
Lanceolate
This leaf is broader towards the base, and
tapering at the apex (about four times as long as
broad). It has the shape of a lance or spear. The
petiole is attached at the broader end. Example:
Nerium oleander.
Oblanceolate
This leaf is broader towards the apex and tapering
at the base (about four times as long as broad).
The petiole is attached at the narrow end.
Example: Banksia serrata.
Falcate
This describes a sickle-shaped leaf. Examples:
Acacia falcata and many Eucalyptus species.
Spatulate
This term describes a leaf with a spatula or spoon
shape, wide at the apex and tapering to a long,
narrow base. Example: Pyracantha fortulleana.
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Oval
This leaf is almost twice as long as it is broad,
with rounded ends. Example: Prostanthera
ovalifolia.
Elliptical
This term describes a leaf shaped like an ellipse,
twice as long as it is broad. Example: Hebe
elliptica.
Ovate
This is an egg-shaped leaf broader towards the
base. Examples: Abelia x grandiflora, Hydrangea
macrophylla.
Obovate
This is an egg-shaped leaf broader towards the
apex. Example: Buxus microphylla.
Oblong
This describes a leaf with length greater than
breadth and sides parallel. The shape is nearly
rectangular with rounded corners. Example:
Coprosma repens.
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Rhomboid
This is a diamond-shaped leaf. Example:
Pittosporum rhombifolium.
Cordate
This leaf is heart-shaped with the petiole in the
indentation at the base. Example: Ceropegia
woodii (string of hearts) and Philodendron
oxycardium.
Obcordate
This means heart-shaped with the lobes
uppermost. In this leaf the petiole is at the sharp
point of the heart shape. Example: Bauhinia
species.
Lyrate
This describes a lyre-shaped leaf, with a large
terminal lobe and smaller lateral ones. Example:
Liriodendron tulipifera (tulip tree) and Ficus lyrata.
Deltoid
This leaf is triangular, broadest at the base.
Example: Populus deltoides.
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Reniform
This describes a kidney- shaped leaf with a
rounded apex. Example: Viola hederacea.
Orbicular
These leaves are circular with the petiole coming
from the centre of the leaf. Example: Tropaeolum
majus (nasturtium).
Cuneate
This describes a wedge-shaped leaf.
Subulate
These leaves are awl-shaped, narrowing to a fine
point. Example: many grasses.
The following terms are used to describe both the shape of the leaf and the leaf margin.
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Bilobed
This term describes butterfly-like
leaves having two lobes.
Example: Bauhinia purpurea.
Trilobed
These are leaves having three
lobes. Example: Passiflora
species.
Palmately lobed
These leaves have a number of
lobes, usually five or seven but
occassionaly more, radiating from
a point in the shape of the palm
of a hand. Example: Acer
palmatum.
Laciniate
This term describes a leaf cut into
narrow, pointed lobes. Example:
Acalypha wilkesiana 'Laciniata'.
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Pinnatifid
This leaf is cut into small lobes
extending less than halfway to
mid vein. Example: Lavandula
spica (lavender)
Pinnatisect
This leaf is cut into small lobes
extending to, or almost to, midvein. Example: Grevillea banksii.
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 Self Assessment 3
Write down the answers to the following questions. When you have finished, check them
against the answers provided at the end of this unit. If you have made any mistakes, revise
the relevant study notes in this unit.
Name the shape of each of the following simple leaves.
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 Self Assessment 3
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 Self Assessment 3
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 Self Assessment 3
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Shapes of leaf margins
The following terms are used to describe the edge of the leaf lamina.
Entire
This means without any division. Example: Nerium
oleander.
Sinuate
The leaf margin has shallow, smooth indentations
on a horizontal plane. The margin is usually entire.
Example: Stellocarpus silluatus.
Undulate
This describes a leaf with a wavy margin on a
vertical plane. Example: Pittosporum ulldulatum.
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Ciliate
The leaf is fringed around the entire margin with
short fine hairs. Example: Tibouchina urvillena.
Serrate
The margin is toothed, with asymmetrical, forwardpointing teeth. Example: Hydrangea macrophylla.
Serrulate
The leaf margin is minutely serrated. Example:
Prunus serrulata.
Biserrate
The leaf margin has minor, secondary serrations on
the major serration. Example: Prunus campanulata.
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Crenate
This margin is characterised by rounded teeth.
Example: Coleus species.
Crenulate
This margin is minutely crenate. Example: many
Camellia sasanqua cultivars.
Dentate
This describes a toothed leaf margin with the teeth
pointing outward. Example: Salix caprea.
Denticulate
This leaf margin has smaller teeth than a dentate
margin.
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The following cross-sections of leaf edges or margins show the various ways in which a leaf
can be rolled at its edge. The purpose is usually to prevent water loss, or conserve water
within the plant, by protecting the stomates. The margin of most of these leaves is entire.
•
incurved
•
involute
•
recurved
•
revolute
•
terete
You should be aware of these margins, although they are not examinable.
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Shapes of leaf apices
Note that 'apices' is the plural of 'apex'.
Acute
The apex forms a sharp angle of less than 90 degrees.
Example: Nerium oleander.
Acuminate
The apex tapers to a point. Example: Hydrangea
macrophylla.
Aristate
This term describes a broad leaf with a long, narrow
tapering point.
Subulate
A long tapering point is typical of a subulate leaf shape.
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Obtuse
The apex forms forming a blunt angle greater than 90
degrees and may be rounded. Example: Metrosideros
excelsa.
Truncate
The leaf ends abruptly as though cut off. Example: Banksia
serrata.
Emarginate
The apex is notched. Example: Alnus glutionosa (alder).
Obcordate
The apex is heart-shaped, with the lobes uppermost.
Example: Bauhinia species.
Retuse
The leaf is rounded with a depression or indentation at the
apex, shallow and rather narrow. Example: Uriodendron
tulipifera.
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Mucronate
This leaf ends abruptly with a sharp point. Example:
Magnolia x soulangiana.
Cuspidate
This term describes a leaf having a sharp, rigid point.
Example: Lambertia formosa.
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Shapes of leaf bases
It can sometimes be difficult to categorise leaf bases
as there are graduations between each main base
type. A leaf base may, for instance, be somewhere
between auriculate and hastate (eg Philodendron
species). Only experience with the bases will enable
you to confidently identify those which are not
typical.
Attenuate
The leaf base is slenderly tapering. Example: Persoonia
attenuata.
Cuneate
This term describes a wedge-shaped leaf base. Example:
Pyracantha fortuneana
Obtuse
This leaf base is rounded.
Oblique
This term describes a leaf where there is more lamina on
one side of the petiole than the other. Example: Ulmus
species, Begonia species.
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Truncate
The leaf base ends abruptly as though cut off.
Example:Populus deltoides.
Cordate
A cordate leaf base is heart-shapedExample: Ceropegia
woodii (string of hearts).
Auriculate
This term describes a leaf base which is shaped like the
lobe of an ear. Example: Ficus lyrata.
Hastate
This leaf base is like an arrow-head with spreading lobes.
Example: Calla aethiopica.
Sagittate
This term describes a leaf base like an arrow-head with
downward-pointing lobes. Example: Young plants of
Syngonium species.
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 Self Assessment 4
Write down the answers to the following questions. When you have finished, check them against
the answers provided at the end of this unit. If you have made any mistakes, revise the relevant
study notes in this unit.
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 Self Assessment 4
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Other morphological features of leaves
There are other morphological features which make recognition of plant species easier and
permit correct and accurate identification.
Leaf venation
This refers to the direction in which the veins of leaves run in relation to the main vein
(mid-rib) and the margin.
Reticulate
A main vein and many lateral and
smaller veins forming a network.
Example: Hydrangea
macroplzylla.
Parallel
The veins are parallel down the
long axis of the leaf, usually all
veins about the same size,
although there is often a central
midrib. Example: Gladiolus
species.
This venation is typical of
monocotyledons, but it also
occurs in some dicotyledons.
Always look further than the venation when determining whether a genus is a
monocotyledon or a dicotyledon. The fact that some species of Eucalyptus and Melaleuca
have parallel venation (which are both dicotyledons) does not mean that they are
automatically classified as monocotyledons.
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Penniveined
The veins run parallel with each
other between the main vein and
the margin. Example: Maranta
species (prayer plant), banana.
Palmate
Several main veins radiate from
one point and typical of simple
leaves with a palmately lobed
shape. Example: Acer species
(maples).
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Leaf attachments
The way in individual leaves are physically attached
to the stem is another characteristic useful in the
identification of species.
Petiolate
This term describes any leaf with a petiole. Example:
Hydrangea macrophylla.
Sessile
A sessile leaf has no petiole so the leaf base is attached
directly onto the stem. Example: Bauera rubioides.
Perfoliate
This describes a sessile leaf with its base completely
wrapped around the stem.
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Peltate
The petiole is attached to the lower surface of the lamina
usually in the centre, not to the leaf margin and is typical
of simple leaves with an orbicular leaf shape. Example:
Tropaeolum majus.
Decurrent
This term is used to describe a leaf with the base
extending down the stem. Example: Gladiolus species.
Sheathing
This term describes a leaf base that forms a tubular
casing around the stem. Example: Many grass species
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Phyllotaxy or Leaf arrangement
This refers to the actual arrangement of leaves on the stem, regardless of how they are
attached.
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Opposite
The leaves are attached at the same level (or node) on
each side of the stem. Example: Angophora species,
Acer species.
Whorled
Three or more leaves are attached at the same level (or
node) on the stem. Example: Westringia fruticosa.
Decussate
The leaves are arranged in pairs alternately at right
angles to each other. Example: Hebe elliptica.
Alternate
The leaves are attached at different levels on either side
of the stem. Example: Abutilon x hybrida.
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Spiral
The leaves are borne at different levels in an ascending
spiral. Example: Callistemon viminalis.
Radical
All the leaves arise from a short stem with internodes
which are very close together, usually at ground level,
can also be called basal or rosette. Example: Gerbera
jamesonii.
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 Self Assessment 5
Write down the answers to the following questions. When you have
finished, check them against the answers provided at the end of this unit.
If you have made any mistakes, revise the relevant study notes in this
unit.
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 Self Assessment 5
Name the following leaf venation, leaf attachments and/or phyllotaxy for
the examples given.
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 Self Assessment 5
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 Self Assessment 5
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 Self Assessment 5
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Leaf surfaces
This is an important aspect of leaf description. You should understand the terms in the
following list and be able to apply them to any given leaf. They are very useful for
identification. They are not examinable.

glabrous
smooth, without hairs. Example: Camellia
japonica

pubescent
downy, having short, fine soft hairs

tomentose
having short, dense hairs, usually matted
together to form a felt-like surface; having
woolly hairs. Example: erastium tomentosum

villous
having long, soft hairs

hirsute
covered by coarse hairs

hispid
covered with short, stiff hairs

scabrous
having a rough surface. Example: Celtis
australis

glaucous
having a blue colour.
Now that you have completed this unit of study you should start work on the Assignment at
the end of this unit and also move onto Unit 3. I hope you are enjoying this work.
Remember that the more you practise, the easier it becomes.
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Answers to Self Assessment questions
Self-assessment 1
A
B
1.
Apex of leaf
2.
Lateral veins
3.
Main vein or mid rib
4.
Leaf margin
5.
Leaf lamina or leaf blade
6.
Leaf base
7.
Petiole
8.
Auxiliary (or lateral) bud
1.
Terminal leaflet
2.
Leaflets
3.
Petiolule
4.
Rachis
5.
Petiole
6.
Auxiliary (or lateral) bud
Self-assessment 2
(a) trifoliolate
(b) paripinnate
(c) trifoliolate
(d) palmate/digitate
(e) imparipinnate
Self-assessment 3
(a) ovate
(b) oval
(c) spatulate
(d) trilobed
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(e) reniform
(f) pinnatisect
(g) pinnatifid
(h) rhomboid
(i) elliptical
(j) lanceolate
(k) falcate
(1) linear
(m) elliptical
(n) rhomboid
(0) elliptical! oval
(p) elliptical
(q) palmately lobed
Self-assessment 4
(a)
lower half: entire
upper half: serrulate
acute apex
(b)
lower half: entire
upper half: serrate
acute apex
(c)
biserrate
oblique
(d)
acuminate
hastate
(e)
mucronate
entire
obtuse
(f)
serrate
acuminate
(g)
palmately lobed (remember with some simple leaf shapes you don't have to worry
about the actual margin)
(h)
finely serrate
acuminate
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(i)
crenate
truncate
(j)
acute/acuminate
obtuse/cuneate
serrate
Self-assessment 5
(a) Petiolate
alternate
(b) Petiolate
opposite
reticulate
(c) Alternate
(d) Opposite
palmate
(e) Reticulate
(f) Sessile
(g) Reticulate
(h) Opposite/spiral
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Appendix Leaf arrangement
Opposite
Whorled
Alternate
Decussate
Spiral
Radical
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Leaf attachment
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Simple Leaf shapes
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Compound Leaf shapes
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Leaf apex types
Leaf bases
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Leaf margins
UNIT 2 Contents
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