Almost all the flowering plants have leaves. A few have phyllodes or cladodes, types of stem that work like leaves. Apart from that, there is a huge amount of variation to look for. They also have a few things in common. Most of the photosynthesis in a plant, the work of food-making, happens in the leaves.
The pictures above show a member of the pea family called Bossiaea (pronounced ‘bossier’). They are hard to find where I live, and these are the best shots I have. Notice how the leaves are reduced to little scales, poking out from the sides of the flattened stem, which is called a cladode.
Leaves also have openings called stomates, which we will come to later. Most leaves are green because of the chlorophyll in them. Chlorophyll is the molecule plants use to capture the sun’s energy to drive photosynthesis. Some leaves are coloured because they contain other pigments that hide the chlorophyll.
Old leaves get their colours because plants break down the chemicals in the leaves and try to take back as much goodness as possible before the leaves fall off. The autumn colours are leftovers. Most leaves have different upper and lower surfaces, but try to find a top or a bottom on a gum leaf!
Most leaves are free to wave around in the breeze, catching as much sunlight as possible, but gum leaves hang down vertically, which is why the two sides are identical.
Image credit: based on a Wikipedia Commons image, Leaf Tissue Structure by Zephyris.
You would never see the picture above under the microscope: it is built up from different views under high-powered microscopes. Ignore the names, but note that there are openings into the leaf, and air spaces inside. The chloroplasts inside the cells are the places where photosynthesis happens.
She-oak 'needles' are really stems that have the leaves stuck onto them. At each 'joint', there are leaf tips sticking out. Some leaves have hairs on them
There are other leaves that are furry.
And then there are the stomates...
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