Friday, June 8, 2012

Crested wood fern

A wonderfully swampy woods at Cedar Bog - full of interesting plants, and mosquitoes! The biting insects are par for the course when exploring such places, unfortunately, but a bit of bug repellent can keep them at bay. Much more worrisome is another bug, the emerald ash borer. Much of this forests's composition is made up of ash, including many hefty pumpkin ash, Fraxinus profunda. As those big trees are killed off by the invasive borer, the ecology of this swamp will be dramatically altered.

One of my favorite ferns grows with frequency in Cedar Bog's shady wet woods, the crested wood fern, Dryopteris cristata. Its blades, or leaves, are long and narrow, and note how the pinnae - fern-speak for leaflet - are short and stubby, and are attached perpendicular to the rachis, or stem, like little stair steps. The overall look is of a very long, narrow, swordlike plant.

These specimens were in full fruit the other day, when I made these photos. Turning the pinnae to see the undersides reveals the presence of copious "fruit dots", which are more technically known as sori. The shape and position of the sori can be helpful in identifying many of Ohio's 100 or so fern species.

A closer view of the crested wood fern's sori. They resemble little bottle caps glued to the leaf surface. The sori are essentially like tiny paper bags that contain numerous round spore cases, in which the spores are enclosed. Click the photo to enlarge and you'll see the cases. Most fern spores are miniscule in the extreme, and are easily windborne and carried to new sites on breezes. They're given a liftoff by the explosive opening of the ripe sori, at least in some cases.

Ferns have certainly been successful. They've been around since the dinosaur days, and long before. Fossilized ferns compose much of the coal that we use, and ferns remain abundant to this day, especially in tropical regions.


Sharkbytes said...

I love the crested wood fern!

Auralee said...

Yesterday, we spent about 6 hours in the fen, Newcomb's in hand, after reading your article on the lady's slippers. Now we know why you're always raving about the place. The lady's slippers had faded but we still saw a few good specimens. Exciting to know that we saw some of Ohio's rarest plants. This would be the kind of place you need to visit every few weeks, just to see what's new! We hated to leave. Thanks for highlighting this treasure!