How were these drawings made? It seems the only accurate way would be to painstakingly excavate soil around the root systems a few tiny clumps at a time so as to record how the root system really is shaped prior to any disturbance. This would mean slowly observing the root system from shallower to deeper levels, then reconstructing the side views seen in the drawings.

Growing the plants in some sort of 2D glass observation vessel in order to observe the roots from the side would cause the roots to grow more unusually than in nature.

Very curious how these were done.