From the yellow mycorrhiza fungus Corticium croceum, a pigment has been isolated for which the name âcorticrocinâ is proposed. Corticium croceum is a symbiont on the roots of Pinus silvestris, Picea excelsa, Vaccinium vitis idæa and other plants. The symbiosis is especially common when the plants grow on a poor, acid, sandy soil or on raw humus.