The Preservation of Favored Traces

A brief aside from ferns: a grad student friend just sent around a link to a really cool web-project based on Darwin's Origin of Species, called The Preservation of Favored Traces. It traces all of the edits Darwin made to the Origin as it went through six editions during his lifetime. This project traces them, color-coding by edition, and if you mouse over it you can read the color-coded edits. It's sort of mesmerizing, and a great distraction if you're a bit of a Darwin geek, or even if you're not...

Hawaii - Lava Tube

One more post about lava; specifically, lava tubes. We visited the famous Thurston Lava Tube in Volcano National park, a giant tunnel left in the surrounding lava by a flowing lava wave that passed through, hollowing out as it went. The entrance to the tube is in a depression that makes a nice little micro-climate for many ferns, which are draped luxuriously around the entrance. Adiantum is the most common fern in these photos:

Once you get inside the lava tube (next picture), you're not done with the ferns... around every one of the light fixtures installed to illuminate the tunnel, spores have germinated and ferns are growing. A testament if ever there was one to ferns' ability to photosynthesize in low light conditions!

With the flash off, and then on:

Hawaii - Lava Ferns

The most conspicuous feature of Hawaii, for someone who has never been there before, is undeniably the lava. The entire terrestrial surface of the islands is made of this stuff, a dark, craggy, ominous-looking substrate which looks suspiciously like it should still be hot to the touch from its eruptive moment of creation. In fact, for much of the lava on the south-east side of the Big Island, in the active volcanic zone, this is almost literally true. Many of these flows were formed within the last century, some of them in the last 30-40 years, and lava is still actively erupting today.

The next thing a newcomer to Hawaii might notice, after oggling the lava, is the green stuff on the lava. That would be the plants. And in most cases, the first colonists and only plants intrepid to live out on this stuff, are ferns. Ferns are excellent dispersers because of their lightweight, durable spores, so they are often the first plants to reach newly-available substrates, like lava. Here's a small sampling to give you a feel for the desolation of the lava, and hopefully, an appreciation for the indomitable nature of the ferns that live on it!

The ferns in the right photo above and at the top of this post are species of Sadleria, and the small ferns in the next photo down are Polypodium pellucidum.

Hawaii - Elaphoglossum

Hawaii has eight endemic species of Elaphoglossum, which are simple, entire-leaved ferns that are often ephiphytic (growing on trees) but can be terrestrial as well. We found two species on our trip, both in a kipuka, an area of lava that is older than the lava around it, and so forms a sort of vegetated island in the middle of an otherwise desolate, young lava flow. Kipuka will often be grassy or forested, and the one we visited was the latter.

One of the species we found was Elaphoglossum paleaceum, which is easy to identify because of its nodding habit and profuse golden scales; it is pictured above and in the next two photos. The remaining photos are of the other species in the kipuka, which had an erect growth form and was not as densely scaly. Its identification was a little less straightforward... I will stick with calling Elaphoglossum sp., at least for now.

Hawaii - Cyrtomium

We found two species of Cyrtomium in the Mauna Loa Bird Park near Volcano National Park. I'm very partial to this genus because it's commonly found in greenhouses and botanical garden conservatories where they want to create a very tropical-feeling environment, but it's rarely labelled. It also doesn't look much like a fern unless you turn it over and notice the sori.

This is Cyrtomium caryotideum:

And Cyrtomium falcatum:

Hawaii - Asplenium

Another important genus of ferns in Hawaii is Asplenium. This group is found throughout the tropics, and there are several species in the Hawaiian islands. Asplenium species have linear sori, which can be found in other genera as well, but they can help you figure out if something could be an Asplenium:

The overall shape of the pinnae in Asplenium can also help to identify them. They are usually once pinnate to twice pinnate, or anywhere in between, as you can see in the photos below.

Hawaii - Dicranopteris

This will be the first in a many-post series about various genera of ferns out here on Hawaii. First up is Dicranopteris, one of the most ubiquitous ferns you'll find at low, moist elevations. As you can see from the two photos below, it will drape itself across large swaths of vegetation, absolutely coating them.

Dicranopteris is really beautiful up close, especially when it's young. Its fiddleheads are purplish, and often sport golden or orangeish hairs or scales:

It has a unique growth pattern, unlike most other ferns. It initially sends up one unbranched frond, with fiddlehead, that unfurls and continues growing upward. Eventually, the upward movement stops and the fiddlehead/bud goes dormant. Just below it, two additional buds emerge and strike out sideways, almost at right angles from the original bud. These grow for awhile until they, too, eventually stop, and the process happens over again. This leads to the draping effect, as the fern basically continuously grows outward. (This description is based on the one in Daniel Palmer's Hawai'i's Ferns and Fern Allies book, published in 2003 by University of Hawaii-Honolulu. It's a great book - get a copy if you're visiting Hawaii or want more information on its ferns.) Another effect of this growth form is that there always seem to be little fronds unfurling somewhere on a Dicranopteris:

You can see its sori in the bottom right photo. The species shown in all of these photos is the only one on Hawaii, Dicranopteris linearis. Incidentally, this is one of the only ferns out here I can identify to species, because there's only one of them. Most of the ferns in the following posts I can only get to genus without a lot more work with the keys.