The Grass tree is a large species of true grass, descended from bamboo, located natively on the Great Plateau, 100 million AD.
At the outer edges of the Great Plateau, the steep, debris-covered slopes are swept by winds bringing seasonal rains up from the Shallow Seas. The heavy rainfall and loose soil make for an unstable surface, prone to mudslides and rock falls. However, in many areas the surface is stabilized by plant life evolved to cope with just such conditions.
This is the age of grass trees. Grasses are hardy plants which reproduce sexually by dispersing their seeds, and asexually (or vegetatively) by spreading out a network of underground stems. Their exposed trunks and leaves regrow from the underground portion of the plant and so can withstand a great deal of damage. The network of grass stems can also stabilize loose soil and consolidate steep slopes. The grass trees form the basis of a whole new ecosystem.
In previous times, bamboo was a type of grass which could generate a hollow stem. On the Great Plateau, many species of grass have the ability to produce resilient stems. The lower slopes are clad with forests of grass trees. Stems grow out over rocky outcrops and form woody-looking creepers, gnarled and tangled, reaching like fingers towards the next pocket of soil. The photosynthetic part reaches upwards, sending out sprays of leaves from the central trunk. From a distance, a grass tree looks like a cluster of conifers growing from a tangle of rooty creepers.
The oceanward slope of the Great Plateau is green with grass trees.
Humid mountain wind will blast upwards through gaps between jagged peaks at the edge of the Great Plateau. Fluffy seeds from the grass trees of the lower slopes are swirled upwards in a white blizzard, eddying between the crags. The seeds bristle with tufts that catch the air and act as parachutes. Here and there, they touch the rock, but if there is no soil to engage their little anchors, they are swept onwards once more. From time to time, at one of these landing points, they pick up a little young silver spider.
A young silver spider will grasp one of the seeds and will use its voluminous parachute to carry both of them aloft. The silver spider, as it rides the gusts of wind clinging to the seed, pays out a strand of silk moored (to get its colony's giant web started) to the rock from which it hitched a ride. Often the seed takes the spider so far that its journey is pointless, but on this occasion the two touch down on the other side of the gorge, where the young silver spider tumbles off and secures the other end of the web strand.
The tiny sliver spiders the cross gorges on grass seeds are only juveniles.
In the summer, as clouds of seeds sweep up the valleys, the juvenile silver spiders are released onto the slopes to catch the wind.
The vast bulk of what the great silver spider webs catch consists of the grass seeds that fill the air (with some additional insects caught as well). All are gathered up and brought into crevices within the mountainsides where they are carefully stashed in great seed mounds to lure in poggles.