The Herbarium of PERSOON in the Rijks Herbarium at Leiden is of the greatest interest in connection with many mycological questions of classification and nomenclature. Many well known mycologists have made a careful study of the types, preserved in the collection and have expressed their opinion in different notes added to the specimens. A comparison of these notes is of the highest interest. The object of the present paper is to bring together the notes that have been added to the different specimens of Polystictus Polyporus, and Fomes. In many cases I added further notes of my own, which I made during the last two years. Many of these notes are based on correspondence I have had with M. BRESADOLA, to whom I sent a great many specimens for comparison. For this and for many other kindnesses, I am glad to offer him my sincere thanks.