It All Starts with Certified P Value MycoMedicinals certified organic mushrooms from Paul Stamets and New Chapter are the finest traditional mushrooms grown anywhere in the world, and are the only commercially available mushrooms with a Certified P Value. P Value is a scientific term for the genetic integrity of the mushroom. When Paul Stamets, one of the world's leading mushroom experts, selects a mushroom from the rainforest, he cultures it in rigorously controlled conditions in his laboratories. The growing mushroom mycelium is absolutely genetically identical with the rainforest mushroom that gave it birth, carrying all of its genetic energy and healing force. Mushrooms not grown in such a rigorous potency-assured manner may be hundreds of generations distant from the purity of their genetic heritage, and thus suffer genetic degeneration and lack of vitality. We certify that all MycoMedicinal mushrooms have a P Value ensuring the fullest healing power and potency.