Swans on Aroidia?
Since I have already established that animal life is absent on Aroidia, how can swans be there? The simple fact is that the Swan of Aroidia is Macroalocasia triangularis, the Swan Arum, illustrated in the thumbnail picture at right. When I originally visualized this plant, my impression was that of a group of swans with outrageous headdresses, all huddled together.
The leaves on M. triangularis are a powdery blue-green in color, while the petioles and main veins are a frosty white. Leaves are produced in a three ranked triangular arrangement, much like those seen on the palm, Dypsis decaryi. In keeping with the scale of plants on Aroidia, the Swan Arum towers to 25 feet or more even without a trunk. Inflorescences are completely hidden by the leaves and usually set semmules by apomixis. The Swan Arum will not hybridize with any other species of Macroalocasia.
Catching the Waves
My next stop was the habitat of a wavy long-leaved plant called Lanceolum bicorrugatum. With prominently speckled and striped petioles and leaves growing in one plane, much as those on Ravenala madagascariensis, the plant was familiar, yet distinctively unique at the same time. A young example of this plant can be seen in the picture at left. Notice the doubly-sinuate leaves and the fibrous remnants of spent leaves still visible at the base of the plant.
Lanceolum does not produce a trunk, but merely grows ever larger as each year progresses. As is true of most Aroidian plants, L. bicorrugatum has an underground tuberlike storage organ from which it grows and regenerates. Inflorescences as are known on Earth are absent, but the plant does produce a single gamete, neither male nor female! This plant is a pure gametophyte, one of five unique plants on Aroidia that each produce single gametes comprising five different sexes. All five different gametes join together to produce a superzygote. This superzygote forms a huge semmule that germinates to yield a plant called Aroidendron, the largest plant on Aroidia and the one known as the "Keeper of the Gate". The genesis and purpose of the extraordinary Aroidendron plant will be featured in a future article.
Lanceolum is found only in the northern and southern subpolar regions, and there grows only on archipelagos that have become anchored to submerged geologic formations. This is exclusive to the subpolar regions because only there do the biological archipelagos remain relatively stationary long enough for underwater roots to take hold of the submerged hills and mountains.
While geologic landmasses do exist on Aroidia, most of them are entirely submerged. Those which are not submerged represent the only xerophytic habitats on the planet. Unlike on Earth, organisms responsible for the formation of mineral-based soil are absent. This means that the exposed geologic landmasses on Aroidia are essentially rocky landscapes with small pockets of organic debris on which only plants adapted to xerophytic conditions can survive. My next stop was one of these islands.
Fans in the desert of Aroidia
Some of the plants that most resemble Earth aroids are found on the geologic archipelagos. These relatively inhospitable islands are few and far between, and the plant life on them is markedly different from that found on the biological archipelagos. One example of a larger plant from this drier habitat is Palmaton, a monotypic genus growing only by the rocky crags of these dry isles. Even there, Palmaton grows near the water line so as to have access to enough moisture to grow as it does.
A specimen of Palmaton can be seen in the landscape picture at right. It is the one with the upright palmately-divided leaves, growing very close to the water. Palmaton has stiff gray-green leaves with bright orange veins and petioles. The leaves are held upright to minimize insolation and water loss.
The exposed rock and lack of soil on these islands makes for a very hot and dry environment, even with the water all around the island. Plants growing here are adapted to store water in specialized tissue, and their leaves have thick waxy coatings to retard water loss. Plant roots here are very aggressive in seeking out cracks in rocks and pockets of organic matter to anchor to.
Palmaton is one of several plants possessing roots that can build up extremely high levels of hydrostatic pressure. These roots have the ability to widen cracks in rocks, and even to split rocks. A small colony of Palmaton can, over years, produce a pocket of gravelly substrate in which to thrive. In so doing, the plants literally make their own niches to grow in!
Being of a monotypic genus, Palmaton reproduces via apomictic semmules and does not produce pollenoids of any kind.
In time, my musings returned to the less familiar genera such as Pinnatidendron. This renewed imaginative exploration revealed more of both the familiar and the unfamiliar. From the Chain Leaf vine to the crimson Melon Flower, all of them were of great interest. . .
Picture credit: LariAnn Garner, Aroidia Research
(Continued in Part VII: Butterflies, Crimson Melons and Chains)