Invisible Seeds
—Michael Penziner, FRNC Docent
Spores found under a fern leaf.
For those times when you'd just like to disappear...
Those of you who have read Harry Potter (and, really, who hasn't?) were probably amused by the thought of a Cloak of Invisibility. Well, you shouldn't be. Think of this: for thousands of years, people understood that for plants to reproduce there must be seeds. Plants had seeds and that's all there was to it. Even as recently as a couple of hundred years ago, that was the situation. So, if plants reproduced by seed, and ferns were plants, ferns had to reproduce by seeds. There was only one tiny little problem with that theory. No one could find the seeds. (We know now that ferns reproduce by spores, not seeds, but they didn't know that then.) So there was just one obvious solution and that was, as hard as it was to believe, that the fern seeds must be invisible. So now the problem became how to collect the seeds. It was finally figured out. The way to do it was that on Midsummer's Eve, you stacked twelve pewter plates together and placed them under the fern, then recited certain incantations (no, we haven't found the exact words but we're still looking). That would make the invisible fern seed fall through the first eleven plates and land on the twelfth. You could then collect them and put them in your pocket. But wait, the reward for doing this is that when putting them in your pocket you could then become invisible yourself. What? You don't think that people actually believed that? Just check out Shakespeare's Henry IV, in Act 2, Scene 1, lines 95-98. One of Falstaff's henchmen attempts to persuade another thief to join them and says, "We have the receipt of fern-seed, we walk invisible." And then there's something that Ben Jonson had written in one of his stories: "I had no medicine, sir, to go invisible, no fern seed in my pocket."
OK, here's the real story. Ferns are among the oldest of vascular plants, 400 million years old, so old in fact, that the issue of sex hadn't been worked out completely. So ferns were asexual in their development. No stamens, no pistils. Just spores, which were of course asexual as well, given that they came from the asexual fern. When the spores fall to the ground, they develop into a small heart-shaped body called a prothallus which, and we haven't a clue how it happens, becomes a sexual body, with a male side and a female side. When ripe, the female side emits a pheromone, which prompts the male side to respond. And on the male side is, no kidding, real, honest to goodness, sperm, just as in animal reproduction. The sperm race around the prothallus to the opening on the female side (called the archegonium) and the first one in wins the race, with the prize of fertilizing the egg cell.
Just thought you'd like to know.
