The outer tissues of a vascular plant called horsetail (a division of ferns) contains abrasive particles of silica—a mineral absorbed from the soil to give strength to the plant structure. In fact, because of their roughness, these plants were once called scouring rushes and were used by Native Americans to polish bows and arrows. Early North American settlers also used horsetails to clean their pots and pans along stream banks—these plants are found in abundance in such areas. You can still see horsetails growing today along stream and river banks, and moist areas, such as ditches. They may not be used as scouring pads anymore, but in herbal medicine, they have been used as a mild diuretic and for the healing of broken bones.

Light (and water, of course) controls spore germination in ferns. Wavelengths in the red range of the spectrum induce spore germination, while wavelengths in the blue range of the spectrum prevent spore germination. The term for the effects of wavelength on fern spore germination is called photomorphogenesis (this is not to be confused with photosynthesis, how light is used to produce energy for a plant to use, or phototropism, how the plant grows in the direction of light.)