If this plant never emerges above the ground (even the flower remains underground unless disturbed by curious botanists), how does it spread its seeds? The seeds would be deposited right on top of the parent.

The article briefly mentions rats eating the seeds, so maybe this plant relies on surface disturbance (animals, heavy rain, etc.) to carry its seeds away?

Or perhaps this plant has no need to spread far and wide, since it depends so heavily on a specific combination of fungus and shrub. It would be futile to spread the seeds outside of this narrow habitable zone.