Category Archives: April

Structure and Parts of a Leaf

No seriously! It’s more complex than you might imagine, and having a common language really helps when talking about the parts of a leaf.

For the avoidance of doubt, leaf refers to both the flat type that you imagine, and the needles and scales found on some evergreens. This is not a complete reference, just the parts that I find most useful.

You’d better get comfortable, this is a long post…

Simple Parts of a Leaf

Parts of a leaf diagram

This is a simplified, generalisation. There are, of course, exceptions and variations. The leaf Blade, attaches to the stem of the plant with it’s Petiole. Quite often you will find a Stipule at the base of the petiole, which is like a miniature leaf arrangement. Within the leaf, there will be at least one strengthening midrib, and veins running from it. The leaf receives water and returns sugars through these.

Identification Categories

When it comes to identifying plants by their leaves, there are a number of areas to consider:

  1. The arrangement of the leaves on the stem.
  2. Simple vs Compound Leaves.
  3. Characteristics of the petiole.
  4. Veins.

1. Arrangement

The arrangement of the leaves on the stem can provide vital clues to the identification of a plant. Indeed, for some plants, it’s even in the name. For example, Opposite-leaved, Golden Saxifrage.

These are the main arrangements you may encounter:

  • Opposite – Two leaves from the same point at each point or node on the stem, growing in opposite directions.
  • Alternate – One leaf attached at each point or node on the stem, each successive leaf growing in opposite directions.
  • Basal – Arising from the base of the stem.
  • Cauline – Arising from the Aerial stem.
  • Whorled or Verticillate – Three or more leaves from the same point or node.
  • Rosulate – The leaves form a rosette.
  • Distichous – Leaves are attached in two rows. They can be either opposite or alternate in arrangement.

As a stem grows, leaves tend to grow in the optimum position for collecting light. This can result in leaves forming a helical pattern around the stem.

2. Simple vs Compound Leaves

So, a leaf is a leaf, right? Well, not exactly. There are simple leaves, and leaves which are made up of leaflets. In deciduous trees, for example, the part which detaches itself from the tree in Autumn (Fall) is a leaf. So in Oak trees, that’s a simple Oak leaf, whereas in Ash trees, it’s a compound leaf with multiple leaflets (see images below).

A simple leaf may be deeply lobed, but as long as gaps do not reach the midrib, it is still a simple leaf. Each leaflet of a compound leaf may have it’s own Petiolule (equivalent of a Petiole) and Stipule (Stipel).

Types of Compound Leaf

  • Palmately Compound – Leaflets radiate from the end of the Petiole, like the fingers of a hand e.g. Horse Chestnut
  • Pinnately Compound – Leaflets are arranged along the main or mid-vein.
    • Odd Pinnate – With a terminal leaflet e.g. Ash.
    • Even Pinnate – Without a terminal leaflet e.g. Mahogany.
  • Bipinnately Compound – The leaves are twice divided. The leaf has a main vein, and further secondary veins on which the leaflets are attached e.g. Silk Tree.
  • Trifoliate – A pinnate leaf with just three leaflets e.g. Clover.

3. Characteristics of the Petiole

Leaves with a stalk (petiole) are said to be petiolate. Those without a stalk, which join straight to the branch are said to be sessile.

Where the blade of a leaf partially surrounds the stem, it is said to be clasping or decurrent. Where the blade completely surrounds the stem they are called perfoliate.

The stipule, where present, is a leaf-like appendage on each side at the base of the petiole. Stipules may remain (such as on roses) or be shed as the leaf expands, leaving scars; Known as stipulations.

4. Veins

Veins, occasionally referred to as nerves, extend into the leaf via the petiole and transport nutrients and water between the leaf and the stem. They also play a mechanical role in supporting the leaf structure. Branching from the main vein are secondary veins, and there can be many more branchings, sometimes leading to a net-like structure.

Leaf Shape Terminology

 

Image Name Description
 Auriculate  Having ear-shaped appendages near the petiole e.g. Arum Maculatum
 Cordate  Heart-shaped, with the petiole or stem attached to the notch.
 Deltoid  Shaped like Greek letter Delta, triangular, stem attaches to side.
 Digitate  With finger-like lobes, similar to palmate.
 Elliptic  Oval, with a short or no point.
 Hastate  Spear-shaped: Pointed, with barbs, shaped like a spear point, with flaring pointed lobes at the base.
 Lanceolate  Long, wider in the middle, shaped like a lance tip.
 Linear  Long and very narrow like a blade of grass.
 Lobed  Being divided by clefts, may be pinnately lobed or palmately lobed.
 Obcordate  Heart-shaped, stem attaches at the tapering end.
 Oblique  Asymmetrical leaf base, with one side lower than the other.
 Oblong  Having an elongated form with slightly parallel sides, roughly rectangular.
 Obovate  Teardrop-shaped, stem attaches to the tapering end; reversed ovate.
 Ovate  Oval, egg-shaped, with a tapering point and the widest portion near the petiole.
 Palmate  Palm-shaped, i.e. with lobes or leaflets stemming from the leaf base.
 Perfiolate  With the leaf blade surrounding the stem such that the stem appears to pass through the leaf.

Leaf Edge Terminology

 

 Entire  Even; with a smooth margin; without toothing.
 Ciliate  Fringed with hairs.
 Crenate  Wavy-toothed; dentate with rounded teeth.
 Lobate  Indented, with the indentations not reaching the center.
 Serrate  Saw-toothed; with asymmetrical teeth pointing forward.
 Doubly-Serrate  Each tooth bearing smaller teeth.

 

Source: Wikipedia, Paul Kirtley at frontierbushcraft.com.

The Parts of a Flower

I’m finding that as I learn more about plants and trees, it’s becoming increasingly useful to understand some of the botanical words and phrases that are used. Not just the Latin names (which are helpful sometimes), but also the parts of plants. So the long long white things with yellow things on the end, become the white Filaments with yellow Anthers.

Parts of a flower diagram

It seems to make it much easier to make myself understood, but also it helps me when I’m looking into a plant or tree, and I find myself reading some of the more scientific resources that you find on the web.

So, I’ve added a glossary for botanical terms that a forager might come across whilst learning their trade, here: http://www.foundfood.com/glossary-botanical-terminology-foragers/. Please feel free to make suggestions, I’ll be updating it as I go.

Parts of a Flower

When it comes to the parts of a flower, I knew what stems and petals were; And I think I vaguely remember the terms stigma and stamen from school (although I wasn’t sure what they were). When the term “Sepal” came up, I have no idea, and yet it is the simplest thing. When a green flower bud opens up, and the cover becomes small leaves that often support the petals.. They are the Sepals!

The Stamen is the “male” part of the flower, which consists of a Filament, with an Anther on top. The Anthers are where the pollen forms to be spread by wind, insect or bird.

The Carpel is the “female” part of the flower, which consists of the Stigma, which receives the pollen, the Style which transfers the pollen to the Ovary, and the Ovary which is where the magic happens. This is complicated slightly, as some flowers have multiple Carpels, which can be referred to as a Pistil. When there only one Carpel, the term Pistil can also be used.