Another epiphytic fern

Species name: Platycerium bifurcatum

Common name: elkhorn fern, staghorn fern

Location: UWO Greenhouse

This species of staghorn fern is native to Australia and the surrounding areas, in tropical rain forests (you can read all about another species of staghorn fern HERE). Staghorn ferns are not parasites despite commonly growing off of other trees; they merely use these trees for support, and gather most of the nutrients they need to survive from the air. They will also commonly grow on dead standing trunks, and are important in helping break down organic material to return it to the soil, a vital process in any ecosystem (but a process that must be exceptionally fast in tropical systems because they are so productive) called nutrient cycling.

All ferns can reproduce in two ways, but most of the time you only notice one of these ways. Ferns are vascular plants, but they are in a group that branched off before the "invention" (the evolution) of seeds. So, like mosses and lycophytes, they reproduce via spore production. This spore production occurs on fertile fronds of ferns (what we call "leaves") in sori (sing. sorus), or the brown powdery masses on the underside of the leaves. Sometimes they're in distinct clusters, and in other species they completely cover the outside bottom surface of the frond. Where the sori and located and what they look like can be an important factor in distinguishing species! When spores germinate, they don't produce more fronds. They produce tiny little plants called "gametophytes" (the frond is the "sporophyte", a plant [-phyte] which produces spores [sporo-]) which produce gametes just like regular plants do. The gametophytes produce eggs and sperm (in higher plants, "plant sperm" is pollen), which fuse together to form the zygote which matures into the sporophyte. Normally, none of us are observant enough to notice the gametophyte, because it is so incredibly small (rarely more than a few millimetres across) but in the staghorn fern they can be up to 3 cm across. I didn't notice any while I was taking photographs, but I also wasn't looking very hard.

The staghorn fern, like many species of fern, produces two different types of fronds. The first type, the sterile fronds, are large and shield-shaped. Their role is to protect the roots of the fern from drying out, and in some species act as reservoirs to catch rainwater. The other type of frond is the fertile frond, which are the long, antler-shaped leaves coming out of the opening in the basal fronds. When one basal frond starts to rot (something which I imagine must happen quite frequently; if they're designed to catch water and protect something that must always be wet, they probably rot away quite quickly!), it is replaced by a new basal frond growing off the roots which you can see in the bottom photo. The production of this new basal frond is incredibly rapid; it can go from being a few millimetres across to a few centimetres across in a week or less.

Ferns as brooms

Species name: Psilotum nudum

Common name: whisk fern

Location: UWO Greenhouse

The whisk fern is in a genus of only two species, one of which is endangered throughout its native range. This species, the "naked" whisk fern, is native to southern Japan but now grows through much of the tropical and subtropical world. It is epiphytic, meaning that it can grow off of substrates other than bare earth, usually other plants (it can even grow on rocks and extract nutrients from the passing air currents and in rain water). It is even known to grow on unused power lines in some areas in Africa! When growing on other plants, it is rarely parasitic and instead just uses it as a prop.

Whisk ferns do get their common name from their most common use: as brooms. The branch-like appendages of the fern would be tied together (unlike most common ferns, the stems are actually quite tough and rigid) then attached to a long stick and used to sweep debris. Aside from the obvious use for this plant, there is at least one use that I was surprised to learn about employed by the Native Hawaiian people: as talcum powder. The spores were collected in bowls, and then used on the skin under loincloths to prevent chafing.

Because of the fact that these ferns are perennial species that are incredibly long-lived (even when you don't just compare them to other species of ferns), there has been much interest in the types of secondary compounds produced in the stems (which are actually modified leaves). There has been the suggestion that the whisk fern might be a goldmine of new antibacterial and antifungal chemicals that could be used in agriculture or medicine.

An epiphytic fern

Species name: Platycerium superbum

Common name: staghorn fern

Location: Dominican Republic

This species of fern is a very popular garden plant for tropical gardens, and indoor gardeners with green thumbs are also causing this plant to rise in popularity in greenhouses. This species of staghorn fern is native to a small area in Australia, but is now propagated and easily grown (without being invasive) worldwide in tropical areas. There are about 15 other species in the genus ranging in origins from South America to Asia and everywhere in between. North America and Europe are the only two continents (assuming Antarctica is a given to be inhospitable to tropical plants) that could potentially have staghorn fern habitat that have no native species.

Anyone who's been to Puerto Plata ("Silver Port" in Spanish; named after the trees that are so common there that have bright green leaves on the top but when they flutter in the wind they flip over to reveal their shiny silver underside) has either seen or has taken a ride on the cable car that goes up the mountain. At the top is a giant Jesus statue (very similar if not identical to the one in Rio; it was actually a gift from Brazil) on a dome that used to be a jail but is now a gift shop, and a protected nature preserve. The people in charge of the nature preserve are trying their best at not only educating the public about native Dominican plants, but also conserving habitat suitable for plants that are incredibly rare worldwide. This species of staghorn fern, while not currently at risk for extinction, is becoming more and more rare due to wild harvesting for the gardening industry. The other danger to any Platycerium species is that they are a type of plant called an epiphyte. This is a plant that cannot live on the ground, and instead needs to live on the side of another plant. This doesn't mean that the epiphyte causes the host any harm; in fact, there is no competition for resources between the two plants at all. The host is merely a "prop" to hold the epiphyte off the ground. With tropical forest destruction occurring at an alarming rate worldwide, the available hosts for any epiphyte (which are incredibly common in the tropics) is becoming a scarcity. The sign in the top photo says "do not touch the plants," and there was actually a representative from the nature preserve that was watching all of the tourists like a hawk to make sure no one touched anything. Aside from staghorn ferns, there were incredibly rare orchids (not in bloom, unfortunately) that were also planted there. If someone had of unknowingly picked them, they might have successfully wiped out the only remaining viable population. That might seem like punishment enough, but that would also come with jail time in most tropical countries. Don't pick the plants!

All ferns are vascular plants, which means they contain phloem and xylem to transports nutrients and water throughout the plant (unlike mosses, liverworts and hornworts, which are non-vascular; you can read about the only profiled non-vascular plant, Marchantia, on my blog so far HERE). They reproduce through the production of spores, not seeds, which need to find a suitable habitat to germinate or else they die. Seeds were a great invention by the plant world; this allows plants to create offspring in less than ideal circumstances and let them go dormant in the soil (or a crevasse of a tree, on a leaf, in a compost pile, etc.) until conditions are suitable for germination. Seeds also have nutritive tissue packaged inside them which gives the plant embryo a sugar, protein and fat kick-start which spores can't provide.