Basically a flower is there to ensure pollination, so a fertilised seed can be produced.
There are many types of floral anatomy, and it's too complicated to go through them all, however most plants conform to a single type, and have basic variations on that theme.
I'll run through flowers that have both the male and female parts, although as mentioned in the last post, not all flowers do.
Right. Diagram time (wooo paint, because I don't have photoshop on this computer!):
(not bad for a paint job, hey?!)
The parts of the flower and their function are outlined below:
Petal: Can be bright and colourful to attract pollinators. Can vary in size, shape and colour depending on what the plant is trying to attract, if anything at all. Usually in plants that are not trying to attract anything, they're reduced in size and dull in colour, if they're even present at all.
Sepal: (The green bits at the bottom of the Petals) Together they make up the 'Calyx', functionally they may be there purely to protect the flower (while in bud), or they may be specialised and look like petals. For example most orchids have a specialised Calyx that looks like petals. Dasies are another example - the center of the daisy is actually hundreds of tiny flowers, while the 'petals' are actually a specialised Calyx.
Receptacle: Is basically the base of the flower, it is the part where most of the other components are anchored.
Peduncle: The stem of the flower, from the base of the Receptacle right down until it attaches to the branch it's growing on.
Now the reproductive bits:
Female parts:
Stigma: The part that catches pollen for fertilisation, and part of the Pistil of the flower. Usually it's sticky and pollen-catching only when receptive to fertilisation. Because of this, if the plant splits up when the male and female parts of the flower are mature, the plant can often avoid many of the problems of self-fertilisation.
Style: The stem the Stigma sits on. This can be long or quite short, together with Stigma and Ovary comprises part two of the Pistil.
Ovary: Found at the base of the style, the Ovary contains the female reproductive parts of the plant, the Ovules. The whole structure from Stigma to Ovary makes up the Pistil. The structure of the Ovary can be quite important for identifying plants; it can have one to many chambers, it can sit above the place where the Petals/Sepals/Stames attach to the Receptacle (superior Ovary), halfway down where they attach (semi-inferior) or below where they attach to the Receptacle (inferior Ovary - perhaps I'll put diagrams up sometime to make that clearer!)
Ovules: Again, there may be one or many hundreds of thousands of these, each having the potential to become a new seed. Not all will be successfully fertilised, think of a pea pod. Sometimes you get those tiny little not-developed peas in there? They're probably aborted seeds, or those Ovules that simply haven't managed to be fertilised.
Male parts:
Anther: The pollen-containing part of the flower. Usually the Anther will split open on maturity, releasing the pollen to allow it to be either carried away by the environment or an animal. What axis the Anther splits open on, or if the pollen just moves through pores etc, is often family or genus specific and can be taxonomically useful.
Filament: The stem that the Anther is found on. Together they make up the Stamen, and this can vary in size, number, shape and position in the flower. Plants that want to avoid fertilising themselves might have the Anthers below the Stigma, to stop pollen from the same flower getting to the Stigma. Or they might have Anthers that sit above the Stigma, but mature either before or after the Stigma becomes receptive to pollen.
So that is basic flower anatomy. Pollen is released by Anthers, aiming to get stuck on Stigmas. But you may have noticed that the Stigma is a long way from the Ovules in the Ovary? How does the pollen get from being stuck on top of the Stigma to fertilise the Ovule in the Ovary? I'll tell you in the next post ;)
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