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




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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.

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.



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.



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

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 off the petiole. There is no rachis present. Example: Schlefflera actinophylla (umbrella tree).


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 cross - section 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.



Spathulate

This term describes a leaf with a spatula or spoon shape, wide at the apex and tapering to a long, narrow base. Example: Pyracantha fortuneana.



Oval

This leaf is almost twice as long as it is broad, with rounded ends. Example: Prostanthera ovalifolia.



Elliptic

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.



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.



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.

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 occasionally 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’.



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, mid - vein. Example: Grevillea banksii.



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.

Serrulate

The leaf margin is minutely serrated. Example: Prunus serrulata.



Sinuate

The leaf margin has shallow, smooth indentations on a horizontal plane. The margin is usually entire. Example: Stenocarpus sinuatus.



Biserrate

The leaf margin has minor, secondary serrations on the major serration.


Example: Prunus campanulata.

Undulate

This describes a leaf with a wavy margin on a vertical plane. Example: Pittosporum undulatum.



Crenate

This margin is characterised by rounded teeth. Example: Coleus species.



Ciliate

The leaf is fringed around the entire margin with short fine hairs. Example: Tibouchina urvilleana.



Crenulate

This margin is minutely crenate. Example: many Camellia sasanqua cultivars.



Serrate

The margin is toothed, with asymmetrical, forward - pointing teeth. Example: Hydrangea macrophylla.



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.


Leaf cross-sections

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.



Shapes of leaf apices


Acute

The apex forms a sharp angle of less than 90 degrees. Example: Nerium oleander.



Emarginate

The apex is notched. Example: Alnus glutionosa (alder).



Acuminate

The apex tapers to a point. Example: Hydrangea macrophylla.



Obcordate

The apex is heart - shaped, with the lobes uppermost. Example: Bauhinia species.



Aristate

This term describes a broad leaf with a long, narrow tapering point.



Retuse

The leaf is rounded with a depression or indentation at the apex, shallow and rather narrow. Example: Liriodendron tulipifera.



Subulate

A long tapering point is typical of a subulate leaf shape.



Mucronate

This leaf ends abruptly with a sharp point. Example: Magnolia x soulangiana.



Obtuse

The apex forms forming a blunt angle greater than 90 degrees and may be rounded. Example: Metrosideros excelsa.



Cuspidate

This term describes a leaf having a sharp, rigid point. Example: Lambertia formosa.



Truncate

The leaf ends abruptly as though cut off. Example: Banksia serrata.





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.



Cordate

A cordate leaf base is heart-shaped


Example: Ceropegia woodii (string of hearts).

Cuneate

This term describes a wedge-shaped leaf base. Example: Pyracantha fortuneana.



Auriculate

This term describes a leaf base which is shaped like the lobe of an ear. Example: Ficus lyrata.



Obtuse

This leaf base is rounded.



Hastate

This leaf base is like an arrow - head with spreading lobes. Example: Calla aethiopica.



Oblique

This term describes a leaf where there is more lamina on one side of the petiole than the other.


Examples: Ulmus species, Begonia species.

Sagittate

This term describes a leaf base like an arrow-head with downward-pointing lobes.


Example: Young plants of Syngonium species.

Truncate

The leaf base ends abruptly as though cut off. Example: Populus deltoides.







1 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


Leaf venation 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 macrophylla.



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.

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).




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



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.



Sessile

A sessile leaf has no petiole so the leaf base is attached directly onto the stem. Example: Bauera rubioides.



Decurrent

This term is used to describe a leaf with the base extending down the stem. Example: Gladiolus species.



Perfoliate

This describes a sessile leaf with its base completely wrapped around the stem.



Sheathing

This term describes a leaf base that forms a tubular casing around the stem. Example: many grass species.




Phyllotaxy


This refers to the actual arrangement of leaves on the stem, regardless of how they are attached.

Opposite

The leaves are attached at the same level (or node) on each side of the stem. Examples: Angophora species, Acer species.



Alternate

The leaves are attached at different levels on either side of the stem. Example: Abutilon x hybrida.



Whorled

Three or more leaves are attached at the same level (or node) on the stem. Example: Westringia fruticosa.



Spiral

The leaves are borne at different levels in an ascending spiral. Example: Callistemon viminalis.



Decussate

The leaves are arranged in pairs alternately at right angles to each other. Example: Hebe elliptica.



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: Gerberia jamesonii.


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: Cerastium tomentosum

Villous - having long, soft hairs

Hirsute - covered by coarse hairs

Hispid - covered with short, stiff hairs

Scabrous - having a rough surface., eg Celtis australis

Glaucous - having a blue colour

Flower shapes and inflorescences


This section deals with the various shapes of flowers and the way these flowers can be arranged as a group to form an inflorescence.

When a flower shape is discussed, it is the shape of the petals and/or sepals (the perianth) which constitutes a flower shape. However, because there are also many flowers which do not fit exactly into any one of the flower shapes, it is quite acceptable to combine more than one shape name to describe a specific flower shape.

If the flower does not have distinct sepals and petals (perhaps only one whorl) then it is the shape of that petal like structure that is described.

Figure 1 - Principal organs of a ‘typical’ flower.


Flower shapes


As you are now aware, the arrangement and shape of the perianth segments (usually the petals) within the one flower structure gives rise to a range of different shapes. Knowing the flower shapes makes identification of some plant species easier and can be used to classify plants into plant families. For example, all flowers which are in family Fabaceae, sub - fam. Faboideae, have a papilionate flower shape. Again, labiate flowers are usually in family Lamiaceae.

The stalk of a single flower is known as the pedicel.




Tubulate

Shaped like a tube, the sides are parallel or nearly so, eg Cuphea ignea (cigar flower).



Salverform

Having a slender cylindrical lower part and opening out flat at the mouth, eg Phlox spp, Plumbago spp. The sides of the lower part of floral tube are nearly parallel.



Funnelform

Funnel - shaped; petal lobes may turn back at the top, but not as flat as salverform flowers. The sides of the floral tubes are not parallel gradually widening from the base to the top of the flower, eg Petunia x hybrida, Hibiscus rosa - sinensis.



Campanulate

Bell - shaped; base of flower is more rounded than funnelform flowers. Flowers normally hang down, eg Abutilon x hybridum (Chinese lantern).



Rotate

Wheel - shaped with a short tube at base and spreading at the mouth; petals free from each other, eg Hibbertia spp. (guinea flower), Tibouchina spp, Lagerstroemia indica.



Stellate

Star - shaped, petals usually free from each other, usually 4, 5 or 6 petals, eg Hemerocallis spp. (day lily), Trachelospermum jasminoides.



Labiate

Having one or more petals forming a lip, eg Prostanthera spp, Salvia splendens. Also bilabiate – having two lips, eg Westringia fruticosa. Flowers with labiate or bilabiate shape are typical of members of family Lamiaceae.



Saccate

Irregularly shaped flower with lowest petal spurred or modified into a rounded sac.

Corolla tube often with a sac - like bulge on one side, eg Grevillea spp., Nemanthus spp.

Calceolate

Shaped like the toe of a slipper, eg Paphiopedilum spp. (slipper orchid), Calceolaria. Flower with large bulge on one side.



Papilionate

Shaped like the wings of a butterfly, eg Lathyrus (sweet pea), Wisteria; made up of three distinct petal types:



  1. standard

  2. wings

  3. keel.

Typical of members of family Fabaceae, sub - fam. Faboideae.

Crateriform

Flowers shaped like a shallow open bowl, saucer, or crater of an extinct volcano, eg Papaver spp. (poppy), roses (single).



Cyathiform

Cup - shaped, and open at the top; more curved at the bottom than funnelform and deeper than crateriform; petals not curving out as in campanulate flowers, eg Cobaea scandens (cup and saucer vine), Tulipa spp.



Urceolate

Urn - shaped, narrow at the mouth and wider below, similar to cyathiform but nipped in towards the top; these flowers are often quite small, eg Erica carnea (spring heath), Epacaris spp, Arbutus unedo, Pieris japonica spp.



Radiate

Petals spreading like many rays from a ‘centre’ of reproductive structures; more petals present than rotate or stellate flowers (eg Mesembryanthemum (pigface) Lampranthus). This term is often incorrectly used to describe the inflorescence of members of family Asteraceae.


Having showy stamens

With these types of flowers, we are describing what we see (which are the stamens) rather than the shape of the perianth. It does not mean that these flowers do not have all the parts of a ‘typical’ flower, it is just that it is the stamens which are obvious and showy. There are two types of flowers with showy stamens.

Conspicuously staminate

Flwers with many conspicuous, often brightly coloured and showy stamens; sepals and petals present but may be small and inconspicuous (eg Melaleuca, Callistemon).



Apetalous staminate

Fowers with many conspicuous, often brightly coloured and showy stamens; flowers have no petals when the stamens are mature (eg Eucalyptus). The petals have been modified into a protective structure which is shed as the stamens expand and the flower matures.


Inflorescences


An inflorescence is defined as a group of flowers borne on one stalk or stem. This inflorescence stalk is called the peduncle. The arrangement of individual flowers on a peduncle gives rise to several different inflorescences.

Some inflorescences can be very difficult to determine—in fact, some may be a combination of two inflorescence types. For example, the inflorescence of Lantana species is an umbellate spike. You may find it easier to identify some inflorescences by studying them before all the flowers are opened, or if the flowers have opened, shake the inflorescence gently and turn it upside down.

You must always locate the flowers that have opened first; that is, the oldest flowers in the inflorescence. This will help to determine the inflorescence type. You will note that the individual flowers on some inflorescence diagrams are numbered. Number 1 = oldest flower, or flower formed and opened first, 2 = second formed and opening flower, 3 = third formed and opening flower—and so on to the youngest flower on the inflorescence.

Types of inflorescence


There are three main types of inflorescence:

  • solitary

  • raceme - type, or indeterminate

  • cyme - type, or determinate.

Solitary

Solitary flower borne singly on a pedicel. They may be formed as a terminal flower or singly in the leaf axils up a stem, eg Papaver nudicaule (poppy), Westringa fruticosa.


Raceme type or indeterminate inflorescences

These are all characterised by having the oldest flower opening at the base of the inflorescence while growth is still continuing longitudinally.

Raceme

A group of flowers attached to the peduncle with pedicels of about the same length; the oldest flower is at the bottom of the inflorescence and the youngest at the top, eg Salvia splendens.



Spike

A racemose inflorescence with sessile flowers (without a pedicel), eg Callistemon spp. (bottlebrush).



Panicle

A branched racemose inflorescence with each whole branch being a raceme. The side branches are smaller racemes. A panicle is a compound raceme, eg Yucca spp.



Corymb

A racemose inflorescence in which all the flowers are ultimately borne at the same level because the pedicels are of uneven lengths. The flowers towards the bottom of the peduncle (that is, the oldest flowers) have the longest pedicels, eg Iberis spp. (candytuft), Spiraea spp.



Simple umbel

A racemose inflorescence in which all the pedicels are equal in length and arise at one point on the peduncle. The flowers are at the same level, eg Hippeastrum.



Compound umbel

An inflorescence made up of small umbels arranged in a larger umbel, the peduncles are equal in length, eg fennel, parsley.



Catkin

A pendulous racemose inflorescence modified for wind pollination. It is a loose spike make up of numerous sessile, usually unisexual flowers. Female catkins usually have long hairy styles and stigmas to enhance pollen interception.



Capitulum (Head)

A racemose inflorescence with sessile flowers on a flattened and expanded peduncle, eg Zinnia elegans.



Each inflorescence consists of two floret types



  • ray florets: a ligulate floret around the edge of a capitulum, has a conspicuous ‘strap’;

  • disc florets: tubular florets in the centre of a capitulum.


Cyme type or determinate inflorescences

These are characterised by having an inflorescence in which the terminal flower terminates the growth of that inflorescence and other flowers arise laterally below it. The oldest flowers are nearest the apex, eg Ranunculus spp. (buttercup), Tibouchina spp.

When the flower arise both sides below the terminal flower sides the inflorescence is a dichasial cyme.

When the flowers arise from one side only below the terminal flower, the inflorescence is a monochasialcyme.


2 The ‘typical’ flower


Flowers come in all shapes, sizes and colours, yet at the same time they have some features in common.

Figure 2 - A ‘typical’ flower


Arrangement of floral parts


Floral parts are inserted on the receptacle of each flower. They can either be arranged in whorls or spirally on the receptacle.

Whorls

In most flowers the calyx, corolla, androecium and gynoecium are arranged in circles or whorls on the axis of the flower, eg rose, Petunia spp, Hibiscus spp.



Spirals

Some flowers have the calyx, corolla, androecium and gynoecium attached at different levels in an ascending spiral, eg Magnolia spp, Ranunculus spp.







TAFE NSW – Western Sydney Institute

Created: 03/06/2013

Version: 1.0


Modified: 03/06/2013



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