It's a little late in the day for me to embark on a career in pteridology. Too many ferns, too little time. There may be a backup option: intimate, private pteridophilia or even pteridomania.
But in fact, empty enthusiasm is no substitute for knowledge. It's mortifying that after all these years of treading upon, admiring and sometimes even transplanting them, I know almost nothing about the Ophioglassales or the Marattiales, the Equisetums (although I can identify both the scouring rush and the horsetail), the Hymenophyllales, the lygodium (which climbs with a twining midrib), nor the aquatic Salviniales. And then there are the twelve thousand separate and individual species of Polypodiales. Although I could not help being aware of polypody ferns -- they're all over the place, sparkling in the understory and thriving in forest clearings -- I could not name the name of a single one save the extremely distinctive and graceful maidenhair and the undistinguished plain (and poisonous) and absolutely ineradicable bracken.
Nor, until I read Robbin Moran's enchanting A Natural History of Ferns (Portland, OR, 2004) did I have a clear idea of how ferns reproduce. Of course I was familiar with the folklore upon which Shakespeare drew -- that the seed of the fern is invisible and confers invisibility. There's a micro-debate on the truth of this imaginative idea in an early scene of The First Part of Henry the Fourth:
Gadshill: We steal as in a castle, cocksure; we have the receipt [i.e. recipe] of fern-seed, we walk invisible.
To which the skeptical chamberlain replies, "Nay, by my faith, I think you are more beholding to the night than to fern-seed for your walking invisible."
Our sometimes clever but often obtuse ancestors, knowing that all plant must have seeds, and that ferns didn't, jumped to the conclusion that fern seeds must be invisible. Well, there's a theory. It took a surprisingly long time for the truth to out. In fact ferns bear very small, sometimes even microscopic spores, visible, at best, as a fine dust. It was not until 1794 that John Lindsay noticed that the spores produced a tiny green growth, nor until 1848 that Michael Jerome Leszczyc-Suminski deployed his microscope to determine that these so-called prothalli produced male and female sexual parts, and that from the union of egg and motile sperm an embryonic plant with roots, leaves, and stems was produced.
It seems like an unnecessarily complicated way to reproduce, but let's not judge it harshly because it's worked very successfully for 345 million years, more or less.
Of all the many ferns of past and present, the one that I would most like to see with my own eyes fell by the evolutionary wayside 225 million years ago and is unlikely to be resurrected in some vegetable Jurassic Park. They're the giant lepidodendrons of the late Carboniferous, tree-size ferns that in the form of coal are very likely providing right now the power for your and my computer.
One oddity of some lepidodendra was that after fertilization they took an unusual (perhaps even unique) path. The plant's root aborted while the burgeoning shoot produced both the usual stem and also a downward-growing rooting organ -- not a true root though it anchored the plant, but a root-like system called a rhizomorph. Because the plant was a monocarp --that is, a plant that grows for many years until mature, then flowers, fruits and dies -- both the upside and the downside of the plant were, so to speak, term-limited. And because the stem went both up and down, above ground and below ground, it was remarkably symmetrical along the axis of the soil.
I wonder how a forest of lepidodendra would have appeared to a modern eye. Very exotic, I imagine. Lepidoptera differed from modern trees in many ways, but particularly in that their trunks were green with chlorophyll rather than bark-brown. I think that a grove of them would have been littered with many uprooted or rather uprhizomorphed plants. Quite a jungle, I should imagine, and quite a delicious menu for the lumbering beasts who feasted upon it.