Taxonomy is the science of classification. Dr Patrick Brownsey from Te Papa explains how botanists use reproductive structures (sporangia), vegetative characters (rhizome and frond shape) and microscopic characters (spore size) to classify ferns.
Point of interest:
- The evolution of land plants diagram featured in this video is found in the article What is a plant?
Taxonomy is the science of classification, and ferns are themselves a group separate from flowering plants, and then within the ferns, there are families of ferns, and within families, there are genera, and within genera, we see species.
The reproductive structures are the important ones for the family characters. When you turn over a fern frond and look at the sporangia on the underside, you will quickly see that they are aggregated together into various shapes and patterns, and those are very important for classifying ferns. Some of them have got their sporangia aggregated together into circles. Other are elongated along the veins, and others are arranged around the margin of the frond, and there is all sorts of variations of this sort, and some of them are protected by a little membranous structure that we call an indusium and some of them aren’t. So all of those characters help us to sort out families and genera of ferns.
And then when we come down to individual species within genera, then we are tending to use more the vegetative characters. We are looking at whether the rhizome is creeping or climbing or an erect rhizome. We are looking at the shape of the frond. Usually fronds are highly divided. The degree to which they are divided, if that is the case, is very important and very constant in the ferns. And then we look for things like whether there are hairs on the surface or not. And then if we have to, we get into microscopic characters, like measuring the size of the spores.
Australasian Pollen & Spore Atlas http://creativecommons.org/licenses/by-nc-sa/3.0
Hedwig Storch http://creativecommons.org/licenses/by-sa/3.0/deed.en
Museum of New Zealand Te Papa Tongarewa