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The first ferns appeared 100 million, maybe 200 million years before the dinosaurs appeared. However, most of those ferns are actually extinct. The oldest fossil records we have of extant ferns are from the Carboniferous geological time (which means they are between 300 and 360 million years old), but many of the ferns we have today — around 10,500 different species — evolved relatively recently in geologic time (in the last 70 million years). The last dinosaurs died out 66 million years ago. In short, the ferns we have today were around for millions of years before the dinosaurs went extinct.

Like plants that evolved later on, ferns have apical growth (which means the mains stem of the plant grows more than the side stems), they have vascular tissue (meaning they have tissue that transport fluid and nutrients internally), and they have megaphylls (which means they have a branching vascular network — also known as veins — and the plants have so-called leaf gaps). But one of the features of ferns that I find particularly fascinating, is that they don’t have flowers, nor seeds. Instead they propagate through spores.

The spores are produced inside sporangia, and sporangia cluster together in what is called a sorus. The sori are visible to us with the naked eye. I like to look for these sori. They look different between different species of ferns.

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Sporangia Most plants have flowers and reproduce through seeds. The ferns do not. They reproduce via spores. The spores are produced inside sporangia, and sporangia cluster together in what are called sori. Similar to what we see on many other ferns, the sori of the Dryopteris segura sits on the underside of the pinnae, which is what the photo above shows. Photo: Martin Høyem
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More sporangia The sori of the Woodvardia fimbriata looks distinctive, they sit next to each other like little railroad cars, or like a chain if you like (that's why Woodvardia are commonly referred to as chain fern). The Woodvardia fimbriata is also identified by how the margins of the pinnules have pointed teeth tipped with tiny spines. Photo: Martin Høyem
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… and more There are 250 species of maidenhair fern, in the Adiantum genus. I have reasons to believe that this one here is an Adiantum jordanii. Its sori are located at the margins of the leaflets. Photo: Martin Høyem
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Fiddlehead This is the unfurling fern frond. They are named fiddleheads because they resemble the scroll at the end of some string instrument’s neck (like the fiddle). They’re also called crozier, after a bishop’s staff, which typically curl at the top like a shepherd’s crook.  Photo: Martin Høyem
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Bulbils Some ferns (maybe all? I’m not sure …) grow these grape-looking things, which is a fern’s way to propagate without using its spores: the bulbil will set root and loosen themselves from the parent plant (or maybe they loosen themselves before they set root). Photo: Martin Høyem

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