Success! Or: The Strange Sex Life of Ferns

OK, so this may not be much to look at, but for a fern geek like me this is exciting stuff.

I’ve DSCN3834been growing and propogating ferns and their ilk since my early teens, and this is the first time I have ever been able to grow tree ferns. The oval green thing in the centre of the picture, and the smaller round one below it, are the first proper leaves of two baby ferns.

They are tiny, the lower one is not much more than 1mm across, right at the limit of my not very advanced camera’s macro setting..

Ferns reproduce with spores. Like us humans (and most multicellular life), ferns chromosomes come in pairs. Spores, however, only have unpaired chromosomes, and when they germinate they grow into a simple plant, a flat, heart-shaped scale-like plant called a prothallus. You can see some prothalli in the second picture, the flat green scales scattered across the centre/top line.DSCN3833

Fern reproduction a little strange. The prothalli grow male and female sex organs, the male ones produce free-swimming sperm, which fertilize the eggs. With chromosomes now back in pairs, the fertilised egg grows into a new fern and the cycle continues.

If you didn’t already know about this from your biology lessons, this is a classic example of alternation of generations.

Tree ferns produce hundreds of thousands of spores each year. It’s a mystery why they reproduce so poorly where they normally grow. My tray initially had hundreds of little prothalli. After a few weeks most disappeared until only a couple of dozen were left. From these came my two ferns.  I might get a few more, but it doesn’t look like it.

Now I know what works I’ll try sterilised earth next time in case fungi or bacteria are killing the baby prothalli. But for now – Yay! Tree ferns!

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