Puffgrass

Puffgrasses are the most successful grasses on Serina during the Pangeacene, and make up the majority of grassland communities across the supercontinent. They are fundamentally similar to ancestral grasses and are mostly low-growing plants which spread by rhizomes along the ground, but differ from most in the structure of their seeds, which are dispersed by wind and covered in a coat of long, white, hair-like filaments giving them the appearance of puffs of cotton, thus their common name. The group originated during the Cryocene, where its furry filaments insulated its flowers and seeds from extreme conditions to survive harsh polar winters and allowed them to disperse over long distances over the tundra by floating on the wind, very much like the cotton sedges of Earth's polar regions. The hardiness of the puffgrasses to harsh environmental conditions allowed them to colonize northern deserts toward the end of the Cryocene and during the Thermocene, where conditions were rarely cool enough to allow the formation of tundra conditions, the puffgrasses survived as a lineage of drought-adapted plants well-adapted to grow in a variety of arid climates, which left them pre-adapted to the widespread desertification which occurred across Serina at the end of the Thermocene. The hair-like integument that sheltered their seeds and flowers now prevented the loss of water, providing advantage over grasses with more exposed flowers and seeds.

above: puffgrass, shown with mature seed pods. Soon, the pods will break apart, each seed covered in long white filaments that catch in the wind and are carried off, hopefully to settle on a suitable patch of soil to colonize and start a new patch.

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Modern puffgrasses diversified substantially and have largely replaced traditional grasses with less refined methods of seed dispersal over much of the world since the end of the Thermocene, particularly the far north and the arid interior, though more primitive grasses may still form the basis of grassland ecosystems in the tropics where the climate is mild and rainfall consistent. Puffgrasses are edible and palatable to grazing animals, their leaves being relatively low in silicates and thus easily digested, but their seeds are less palatable as a food source being as they are covered in thick coats of sticky hairs which must be plucked away before the seed is to be consumed. Seed-eating birds are thus less common in the Pangeacene and many which do exist exhibit adaptations different from earlier counterparts; namely, their beaks are longer and thinner, suited to stripping off the hairy seed coats and then swallowing the seed whole rather than adapted to crushing and shelling it before consuming as works for other types of grass seed. Molodonts, seed-eating tribbetheres specialized to feed on hard-shelled seeds and nuts, are not adapted well to process puffgrass seeds as a food source, but nevertheless can skin them of their protective fur coats with their paws and then crush them in their jaws. Tribbetheres and to a lesser extent nesting birds gather the seed coatings as a soft and insulating nest lining.

Though ancestrally desert-adapted, some puffgrasses today thrive in a very different environment - namely, the sea shore. On low-lying floodplains and salt marshes, where tides regularly sweep in and out, puffgrass forms dense monocultures. Here it tolerates even brackish water and submersion for days at a time. Salt-tolerant puffgrasses stabilize the soil and prevent erosion, collecting sediment in their roots. Their presence holds the mud in place, preventing it being washed away by wave action, and as their roots spread down into the substrate they allow oxygen to penetrate so that over time other less hardy plants can establish themselves. As the sediment amasses, it rises above the level of the tides and can then be colonized by terrestrial plants over a process known as succession. Puffgrasses are thus important land-builders, extending coastal habitats into the sea and over many years raising entirely new islands and peninsulas out into the sea. These biomes are highly productive as a result of the regular influx of water-borne nutrients brought in by the tides, but largely lack terrestrial grazers due to the difficulty of the terrain to navigate and lack of fresh drinking water. As a result, the grasses typically break down after death and return immediately to the surrounding sediment, where they provide food for microorganisms which in turn feed invertebrates, small fishes and eventually birds.