squeeze tube (one-way single-use communication device) and worm tunneling
Each strand of corn silk is connected to a single ovule, or potential kernel, on an ear of corn. The ovule to which each strand is connected is identified and inventoried. The tassel at the top of the stalk contains grains of pollen. Fertilizing an individual silk thread with pollen ensures that the ovule to which it is joined will grow into a kernel of corn. The code is written by introducing grains of pollen only to the select silk threads. With this in mind, rub some of the pollen carefully onto the ends of select silk strands extending from the top of the ear. Over time, the message takes shape under the covering of the husk. After maturation, the ear is removed from the stalk and makes its way to the recipient who peels away the husk to decipher the message it holds.
Collected accounts of foxhole radio materials:

Bayonets into the ground
Burnt tree bark
Candle wax
Clothes line
Flour with palm oil
Newspaper soaked in coconut oil
Pencil lead
Razor blade (rusty or “blued” by heat)
Safety pin
Scrap motors (and other found devices)
Tin can
Tin foil
Zinc trouser buttons
waves (air)