The root tunnel held its silence .
Five practitioners . Held breath . The specific quality of biological systems that had been instructed to reduce their acoustic output to the minimum available level and had complied — the breathing calibrated to the shallowest register that the body's oxygen requirement permitted , the heartbeat's transmission through the root system floor the one variable that could not be voluntarily suppressed and was therefore accepted as the one remaining risk that the formation could not eliminate .
Rapax's finger pressed to his lips .
The gesture communicating what the gesture had communicated since before any practitioner present had been born — the oldest available signal for the oldest available instruction . Silence . Not as a preference . As the only available option .
The sound continued its circuit above the canopy .
