Root mat
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| Anatomy | |
|---|---|
| Part of | Beckon |
| Position | Soil around and between Beckons |
| Extent | Tens to a few hundred metres per Beckon |
| Depth | Mostly the top metre of soil |
The root mat is the underground part of a Beckon: a network of strands and blood vessels in the soil around it that digests organic matter, stores biomass, carries the circulation, and joins the Beckon to its neighbours and to Dispatchers. Ground that a root mat has entered is called infested ground. The mat pulses with the beat of the heart, smells of ammonia, and glows faintly green at night.
Structure
Around a large Beckon the mat extends from tens of metres to a few hundred metres, densest in the top metre of soil and thinning with depth. It is made of fine strands that run through the soil in the manner of fungal mycelium, and of thicker vessels that carry blood to and from the root crown at the base of the trunk. Nerve fibres run alongside the vessels. Where the mats of two Beckons meet they join, and the vessels of one Beckon connect to the other's.
Beckons of the Pontic genome, around the Black Sea, share very large mats between many Beckons.
Functions
Digestion
The mat digests organic matter outside the body. Its strands release enzymes into the soil and absorb what they break down, as fungi do. Field organisms that return to a Beckon are reabsorbed into the mat with the biomass they have eaten, and are its main source of food. The digestion of protein releases ammonia and amines, which give infested ground its smell.
Minerals
The mat dissolves soil minerals to obtain the fluoride and sulfate that the gas glands use, and is the means by which an Adapted Beckon refills its gas cells.
Storage and production
The mat holds the Beckon's stored biomass, from which it produces field organisms. Eggs made in the bulb pass down the spine into brood chambers in the mat, where they develop and emerge from the ground. The Deterrents of a Dispatcher on the mat are kept in it between uses.
Circulation
Blood leaves the root crown into the mat and returns to it. The vessels of the mat contract in waves timed to the heartbeat, once every two to five minutes, and the pulse can be felt and heard on infested ground.
Glow
The mat near the surface carries the same fluorescent pigment as a Beckon's outer tissue, driven at night by a light-producing reaction, and glows faintly green as the mycelium of some fungi does. The glow is brightest where the mat is most active. Ground that has been cleared of Beckons often continues to glow, from mat left in the soil.
Spread
A root mat extends outward from its Beckon into uninfested ground, and new Beckons grow out of the ground it has taken. Concrete and other structures in its path are made passable by Grafters. Ground cleared of its Beckons is usually reinfested from the mat left in it.
Control
The mat cannot be poisoned through the soil: substances it absorbs pass through the filtering organ in the bulb before they reach the rest of the body. It is destroyed by excavation, by fire and by heat, and cleared ground is monitored for regrowth. Field teams locate buried mat with geophones, by the pulse.