Banks Peninsula fork fern facts for kids

The Banks Peninsula fork fern (scientific name: Tmesipteris horomaka) is a special type of fern ally. It is found only in New Zealand, meaning it is endemic there. This fern is often called the Banks Peninsula fork fern because it was first discovered in that area.

What it Looks Like

The Banks Peninsula fork fern often grows on the stems of other plants, especially tree ferns. When it grows on other plants, it's called an epiphyte. Sometimes, it can also be found growing on the ground, or on rotting logs. When it grows on the ground, it's called a terrestrial fern.

Many stems of this fern can grow on one tree fern. It has a root-like part that creeps along, called a rhizome. From this rhizome, many new shoots can grow. The stems that grow into the air can be quite long, from about 6 to 51 centimeters (about 2.4 to 20 inches) tall. They are usually about 1.5 to 3.5 centimeters (about 0.6 to 1.4 inches) wide.

The leaves of Tmesipteris horomaka are rounded at the top. They have a small, sharp point called a mucron at the very tip. These leaves are usually 1 to 2.5 centimeters (about 0.4 to 1 inch) long and 0.25 to 0.65 centimeters (about 0.1 to 0.25 inches) wide.

This fern looks a bit like two other related ferns, T. elongata and T. tannensis. However, T. horomaka is different in a few ways. For example, the way it produces spores is different from T. tannensis. It also has leaves that are flat at the top with a small dip, which is different from T. elongata. Another key difference is its spore size. While its parent ferns have two sets of chromosomes (tetraploid), T. horomaka has four sets (octoploid).

Where it Lives

Tmesipteris horomaka mostly grows as an epiphyte. This means it hangs from the trunks of tree ferns or other trees in the forest. It uses these trees for support.

When it was first found, T. horomaka was seen growing on the stems of tree ferns. However, one sample was also found growing on decaying flax plants on a cliff face. The types of tree ferns that can host T. horomaka include Cyathea dealbata, C. smithii, and Dicksonia squarrosa. These tree ferns are found in different types of forests in New Zealand, like podocarp, broadleaved, and beech forests.

So far, this fern has only been found in New Zealand. Most of its population is in the Banks Peninsula area and the Port Hills near Christchurch.

How it Lives

Life Cycle and Reproduction

Ferns are vascular plants, meaning they have special tissues to carry water and nutrients. Their life cycle has two main stages. First, there's the sporophytic phase, which is the fern plant you usually see. Then, there's the gametophytic phase, which is a tiny, often unseen stage.

The fern produces tiny reproductive cells called spores. These spores are found in special organs called sporangia, which are usually on the fern's leaves. A small number of these spores are carried by the wind. If they land in a good spot, they can grow into a tiny plant called a gametophyte.

Fertilization happens when male and female cells, produced on different gametophytes, come together. The new plant, called an embryo, then grows inside the gametophyte. Eventually, the embryo starts to divide and grow, leading to the development of a new fern plant.

How it Gets Food

The rhizome of this fern is not a true root. It cannot make its own food through photosynthesis because it doesn't have chlorophyll. The rhizome is covered in tiny, golden-brown hairs called rhizoids. Scientists believe that this fern gets extra nutrients from a special type of fungus that lives inside its tissues. This is a common way for some plants to get food.

Threats to the Fern

The Banks Peninsula fork fern is considered an endemic species, meaning it's only found in New Zealand.

The Department of Conservation once considered Tmesipteris horomaka a threatened species. This meant it needed extra help to survive. At one point, there were thought to be fewer than 250 mature individual ferns. This number would put it in the "endangered" category. However, more surveys are needed because it's a newly discovered species. So far, the biggest threat to this fern is the safety and survival of the host plants it grows on. If its host trees are removed or damaged, the fern is also at risk.

Other Interesting Facts

Tmesipteris horomaka was discovered by researchers Leon R Perrie and Patrick J Brownsey. They were studying the chromosome numbers of two other Tmesipteris species when they found this new fern on the Banks Peninsula.

This new species was a natural cross between two local ferns, T. elongata and T. tannensis. The new fern had characteristics that were quite different from its parent plants.

The tiny gametophytes (also called prothalli) of this fern are very hard to find in nature. This is partly because of where Tmesipteris plants grow, how dense their populations can be, and how long they stay dormant before growing into a full plant.