Flora of the Middle Muricene, Part 2

Rat-grasses, woodlouse-grasses, and basket-grasses are powerful shapers of ecosystems, creating unique environments through their growth habits, interspecies relations, and reproductive strategies. Each has powerful knock-on effects for all other life on Apterra, directly or indirectly determining who will survive and who will go extinct. In their shadows grow thousands of species belonging to various minor (or formerly so) lineages of Apterran plants. In the Early Muricene, most of these were odd offshoots, footnotes in the story of the other grasses' rise to power. Despite this, each of them has altered their world in subtle ways, in some cases even reaching ecological dominance in their own right. 

At high latitudes and high elevations, spiny-grasses reign supreme as the dominant non-pseudotrees in their frigid habitat. Spiny turfgrasses (Cryopoa) cover the permafrost, preventing erosion and insulating a layer of warmer, fertile soil between themselves and the ice below. Sharp thorns tip their surprisingly nutritious foliage, an ample food source for any animal with the proper adaptations to consume it. Meanwhile, their larger rhizomatous cousins (Occumbophytum) grow up to a meter high before collapsing, then proceed to grow new stems from the fallen stalk. In this way, they grow exponentially in size every time they're damaged, being kept in check only by tough-beaked grazers that snack on them. On the whole, though, the spiny-grasses are in decline. Other generalistic plants, such as the thorny barrel-grasses and rat-briars, are beginning to gain ground in the competition for arctic dominance.

More derived members of the group, on the other hand, have begun to establish themselves outside their ancestral niches. One member of the rhizomatous group, Occumbophytum fortis, has strengthened its stalk into a more permanent structure. These grow in clumps of many individuals up to ten meters wide, with each plant reaching about a meter high. This Spine-Brush provides shelter in cold regions, serving as a safe hideaway analogous to the rat-briar/palm-brush thickets of warmer climes.

This tough-stemmed morphology is taken to even greater extremes by grasses like the desert-dwelling pillar-spine (Latispinus), whose culm is nearly 20 centimeters in diameter, with short, sharp blades providing defense against herbivores who might otherwise enjoy a meal of the plant's soft, delicious stem. In temperate pseudoforests, the holly-grass (Ilexophyllum) similarly deters would-be grazers with its short, round, many-thorned leaves.

The largest of the group is the spine-stalk (Polyramus), a three-meter pseudotree with numerous branches splitting from a central trunk. Each is lined with many small, sharp blades, giving the appearance of larger, palm-like fronds. These are a minor component of boreal pseudoforests, facing fierce competition with wax-palms and cold-hardy basket-bushes. 

Clinging to riverbanks and scattered across temperate rain-pseudoforest floors, fern-spines (Blachnomimus) bask in dappled sunlight. Unlike the former genus, these possess large and truly pinnate leaves, arranged in a neat basal rosette around a compressed stem. With a spine on each leaflet, few herbivores dare attack a fern-spine. Beneath their canopy, therefore, is a useful refuge for small prey animals, serving a similar role to the spine-brush but on a much smaller scale; fern-spines reach no more than half a meter in diameter, greatly limiting the size of creatures who can take advantage of their protection.

The final member of this group, while closely related to fern-spines, does not provide a safe microhabitat to the fauna of its prairie home. On the contrary, it is specialized to take advantage of the unique microbiome within large keg-grasses. These keg-spines (Doliohabitus) resemble small fern-spines, sharing their tolerance for low-light conditions. Direct sunlight reaches the bottom of the keg-grass for only a few hours each day, and that's all these grasses need to survive and outcompete other keg-dwellers. This genus is often the first to colonize young keg-grasses once they reach suitable sizes, growing rapidly after their tiny seeds drift in on the wind. As they are quite nutrient-hungry, after a single season they have exhausted their food supply. In response, they grow a five-meter-tall inflorescence, release up to 20,000 seeds, and promptly die, allowing other plants to grow within the keg for many more years.

Tropical oddballs tend to fare quite well, as the productive ecosystems of Apterra's various equatorial regions still have many vacant niches. The chain-grasses (Catenophyllum), for instance, with their asymmetrical leaf arrangement, have become common in Abelian and Sub-Abelian rain-pseudoforests, having become a ubiquitous understory plant due to their fast rate of recovery from grazing. Having more nutritious foliage than basket-grasses (their primary competitors), they are a staple dietary component for herbivores with more selective preferences. Stalked forms may reach upwards of two meters, while more compressed species lie low against the pseudoforest floor. 

The most successful member of this genus, though, is the Chainana (C. musamimus), a tall but stalkless species that can rival basket-bushes and palms of paradise in its height. Each petiole forms a cylindrical sheath that rises up to six meters off the ground, tipped with a flowing, serrate leaf. New leaves grow in the middle of the old ones, pushing outwards and upwards until the outermost layers crack open. From above, the chainana's canopy is spiral-shaped, with each new leaf a few degrees offset from the previous one. 

Like the first chain-grasses, this species produces immense quantities of tiny seeds, releasing them during heavy rains in hopes they'll be washed into streams and rivers. There they'll be eaten by fish, remain in their guts for up to a week, and be deposited on the riverbank, potentially many miles from their parents. This limits the range of all chain-grasses to solely locations that are at least occasionally inundated with water. In the humid tropics, that includes all but the highest hills, but this trait severely restricts the genus's expansion into drier environments.

In drier pseudoforests, a different chain-grass has come to dominate - one that disperses easily over dry land thanks to its partnership with small birds. The Stairstem (C. scalarius) has a single vertical stalk that supports a series of sturdy, strap-like leaves that can support up to a kilogram of weight. These blades are attached horizontally and overlap slightly, providing an easy route for scansorial birds like skeeter-snappers and some pillbirds to reach the seeds at the top of the plant. The grains are much larger than those of other chain-grasses, possess chemical defenses that render them toxic to mammals, and can pass through the avian digestive system intact. Only a few birds can actually crack the seeds; most of those that visit the stairstem are actually in search of the lipid-rich glumes that surround the grains. They swallow the entire structure, digest the outer covering, and excrete the seed in one piece.

Originating from the Gecko Isles, paddle-grasses have not seen success in the Middle Muricene. While their sturdy forms were useful millennia ago, giving them an edge over weaker beach-dwelling grasses, other groups (for example, windswept skystalks) have since found more energy-efficient means of achieving the same results. No longer competitive in its original habitat and finding itself unable to branch out into new forms, the paddle-grass lineage was lost to time somewhere around 750,000 PA. Hydrostalks have similarly lost out to fitter genera over the generations. Their soft, unprotected tissues are simply unable to withstand the pressure of mainland grazers, leaving them relegated to the smallest, grazer-free isles, where they persist in small numbers as insular megaherbs. Fan-grasses too have been a casualty of the current geological age; though they remain a significant presence on the Isles, they simply cannot survive competition with mainland pseudotrees. Overall, the unique flora of the Gecko Isles has proven incapable of holding its own against the changing world of the Middle Muricene, failing to find a place for itself in the ecosystems of modern Apterra.

The Dawn Muricene vine-like climbing grasses have risen to greater prominence in the world of today. With the rise of tall pseudotrees and densely wooded areas, they are no longer restricted solely to mountainous regions with bare stony outcrops. Now, the Bladevines (Acutipampinaceae) are a family with hundreds of species. Basal members like the Rockcreepers (Acutipampinus) still cling to rock faces across Apterra's mountains. They are especially common in temperate rain-pseudoforests that form on the seaward side of mountain ranges, while they find less success in rainshadows. Sticky roots weave their way into fissures, anchoring the plant firmly into the stone. Older plants may even shatter boulders after years of built-up pressure from their ever-growing root systems. More often, though, they serve to stabilize loose gravel on steep slopes, helping to prevent landslides and slowing the erosion process. 

On the savanna, tall canopy-palms stand alone; often there can be a kilometer or more from one pseudotree to the next. The local bladevines, therefore, must find a creature that can give their seeds a ride from one palm-grass to the next. The genus Evellophilus, for instance, relies on pillbirds to disperse its seeds. By growing amidst the dense, woodlouse-choked foliage of the canopy-palm, they place themselves directly in the path of insectivores that might brush past the hanging vines, at which point their tiny, spiked grains embed themselves in the bird's plumage. When the pillbird arrives at another food source, some of these hitchhikers may fall off. In some instances, they are deposited within the palm-grass's canopy and can therefore immediately begin the process of overtaking their host. If, on the other hand, they end up on the ground nearby, all is not lost; the sprouts can find the pseudotree by growing toward its shadow until they reach its trunk, at which point they switch to seeking bright light.

Denser pseudoforested areas don't require such extreme measures; it's nearly guaranteed that a suitable host plant will be within a couple meters of any newly-sprouting bladevine. Herbivores, though, are a serious threat. The long, soft stems of bladevines make a tasty snack for many browsers, so many of them have evolved to deposit abrasive silica particles in the tissue of their vines. This allows genera like the Shadeblade (Umbrolamina) to thrive here, only threatened by the most dedicated or desperate plant-eaters.

All vines are, to an extent, parasites of the larger plants they grow upon. They weigh the pseudotrees down, steal a portion of the light that would otherwise land upon their leaves, and if left unchecked can even kill their own hosts. Most bladevines strive to inflict as little damage as possible, as destroying their home would inevitably lead to their own death. One, though, embraces its nature as a killer. The Stangler Bladevine (Strangulamina) grows dozens of branches from its main vine, enveloping the basket-bushes it has evolved to parasitize. Wrapping around each of the basket's large, thick blades, the strangler envelopes its target. The basket-bush soon dies, then begins to rot from the inside out while still standing. At this point, the bare, lifeless trunk is entirely covered by the bladevine, which sends its roots deep into the decaying tissue, absorbing nutrients released during the decay process. When it has fully exhausted its food supply, it flowers, dropping thousands of pea-sized grains onto the ground below. Its life's purpose complete, the strangler dies a few days after the last seeds fall.

Apterra's desert-grasses were originally a group of short-lived plants that grew quickly in response to short rainy periods in the ten-year desert. Many members of the group still live similar lives, such as Psammapoa, an annual turfgrass that sprouts, grows, sets seed, and dies back, all within a two-month period of intense rain that occurs in its south-Abelian habitat. Others, like Abscondophyllum, survive dry periods as underground rhizomes, sprouting rapidly when rain returns. However, not all of Apterra's deserts are prone to such bouts of heavy rain; in many areas, the land is consistently dry year-round, with scant rainfall occurring at random intervals. In these environments, grasses dependent on cycles of inundation are not viable, so the desert-grasses have evolved some new innovations that have allowed them to expand beyond their previous limitations.

The most derived desert-grasses are the Wellstalks (Calorhiza), a genus ubiquitous in the most truly desolate of the planet's deserts. Their taproots are long and thick, reaching up to five meters below the surface. This allows them to draw water from deep aquifers; in areas where this groundwater is especially abundant, they flourish as if they were living in a rain-pseudoforest, displaying bright greens quite uncharacteristic for such otherwise-barren landscapes. Species that grow in regions without extensive subsurface moisture are less extravagant, but they still find great success due to their other water-saving adaptation.

All wellstalks employ crassulacean acid metabolism to conserve water. During the day, they close off their stomata, reducing the amount of water they lose through evapotranspiration and ensuring they don't dry out in the desert sun. When night arrives, the stomata open, losing only a small amount of water to the cool air. At the same time, carbon dioxide diffuses into the plant's tissues, being converted into malic acid for short-term storage. After building up this carbon-rich acid all night long, the stomata close once more in the morning. The stored malate is then gradually reconverted into CO2, fueling photosynthesis throughout the day until the supply is exhausted. 

By conserving water in this fashion, wellstalks have succeeded where no other Apterran grass has managed so far. By being the first to stumble upon this biochemical mechanism, they've given themselves a head start over the dozens of other lineages that will develop CAM photosynthesis in the future. For the time being, they have no competition in their environment, allowing them to diversify quickly. While the wellstalks all appear like rather normal grasses, their isolation and newfound lack of competition may lead them to experiment with more derived forms in later ages.