Precise Distribution of Mercurialis perennis according to Soil Hydrogen Ion Concentration

Abstract

IN a wood covering several acres on the Lower Greensand of Surrey, Mercurialis perennis (dog's mercury) appeared to be distributed in an irregular way, in patches which clearly were not determined by the light intensity alone. In one case it was abundant along the lower side and absent along the upper side of a track that ran across a gentle slope. The pathway had been made up with chalk, and it was clear that the sandy soil below the path had become a possible habitat for Mercurialis because of the washing down of solid calcium carbonate and probably of dissolved bicarbonate as well. The whole region covered by the wood bears scattered patches of chalky soil, owing to transport of chalk for agricultural use and in making up trackways.