Excerpt from Blister Canker of Apple Trees, a Physiological and Chemical Study: A Dissertation Submitted to the Faculty of the Ogden Graduate School of Science in Candidacy for the Degree of Doctor of Philosophy, Department of Botany It is now generally recognized that among the most important problems of plant pathology are those connected with the physiol ogy of diseases whose etiology is already known. It is also recog nized that this must be the physiology of the host, of the parasite, and of the two in relation to each other, and, further, that such a comprehensive View of all the factors involved furnishes the only rational approach to an understanding of the principles underlying immunity and disease resistance. In the present paper are given the results of a physiological study of the destructive disease known as Illinois or blister canker, the etiology of which, including the identity of the causal organism, Nummularia discreta (schw.) Tul., was worked out by hassel bring (22) in 1902. The work reported here is a continuation of an earlier investigation by the writer (30) on the oxidase activity of healthy and diseased bark; in addition there is included an account of the catalase activity and microchemical and macro chemical analyses of both kinds of tissues. Further work is planned on the chemistry of the disease, on the role of other enzymes than. Oxidases, and on the physiology of the fungus itself in pure culture. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works.