During the manufacture of paper living organisms may be the cause of undesirable slime deposits (consisting of bacterial colonies and fungus hyphae) in the machines. An extensive literature on this subject has accumulated and many of these fungus species have been isolated and described. The aim of Mrs. Wang's investigation is not only to determine the species and their frequency in pulp and paper mills in New York State, but also to provide a compendium describing and illustrating the fungus species in order to facilitate their recognition by workers in this field of microbiology and mycology. Following a “Review of Literature” and a chapter on “Materials and Methods” there is a chapter entitled “Results and discussion”. The bulk of the contents, however, consists of the isolated species: Phycomycetes (8 species), Ascomycetes (6), Basidiomycetes (8), Fungi imperfecti (86), and Actinomycetes (7). Of each species at least one and very often many cultures were studied. The descriptions of the colonies are clear and in conjunction with the illustrations they should enable future workers to recognize the species described. To this Penicillium forms an exception since no descriptions and illustrations of this genus are given; Raper & Thom’s manual on the genus is referred to. With a few exceptions the photographs reproduced on the text-plates are of cultures on plates. A lengthy bibliography is added.