Translations:Manfred Klett: Von der Agrartechnologie zur Landbaukunst/1576/en

The life process of the horsetail is a metabolically active silica process, born out of the element of water. It moves from within outward toward the periphery of the living tissues. As the water evaporates through the outer warmth, the silica is precipitated and envelops the entire stem-plant in a mantle of water-bearing, amorphous silica. It is found in the epidermal cells as well as deposited between the cell membranes of the same. All states are passed through — from that of solution, through the plastic gel, to the hardened, amorphous, glass-like opal — a water-bearing silicon dioxide (SiO₂ + H₂O). When the stem-herb of the horsetail is incinerated, after the combustion of the black carbon skeleton there remains at last a white silica skeleton. It shows lens-shaped protrusions which, in the living state, direct sunlight onto the chlorophyll arranged in rows.