EX-OFFICIO MEMBERS OF THE EXECUTIVE COMMITTEE Past Presidents still retaining membership in the Society R. H. WARD, M.D., F.R.M.S., of Troy, N. Y., at Indianapolis, Ind., 1878, and at Buffalo, N. Y., 1879. Albert McCalla, Ph.D., of Chicago, Ill. T. J. BURRILL, Ph.D., of Urbana, Ill., at Chicago, Ill., 1883 at Chautauqua, N. Y., 1886, and at Buffalo, N. Y., 1904. GEO. E. FELL, M.D., F.R.M.S., of Buffalo, N. Y., SIMON HENRY Gage, B.S., of Ithaca, N. Y., at Detroit, Mich., 1890. at Ithaca, N. Y., 1895 and 1906. A. CLIFFORD MERCER, M.D., F.R.M.S., of Syracuse, N. Y., C. H. EIGENMANN, Ph.D., of Bloomington, Ind., A. E. HERTZLER, M.D., of Kansas City, Mo., at Pittsburg, Pa., 1896. at New York City, 1900. at Denver, Colo., 1901. at Pittsburg, Pa., 1902. at Winona Lake, Ind., 1903. at Sandusky, Ohio, 1905. at Minneapolis, Minn., 1910. at Washington, D. C., 1911. at Cleveland, Ohio, 1912. The Society does not hold itself responsible for the opinions expressed by members in its published Transactions unless endorsed by special vote. TABLE OF CONTENTS FOR VOLUME XXXII, Number 1, January, 1913 Dissemination of Fungi Causing Disease, by F. D. Heald (Presidential Periodicity of Algae in Illinois, 8 Text Figures, by Edgar Allen Transeau Nature and Classification of Plant Rusts, 5 Text Figures, by Frank D. Notes and Reviews-Notes on Some Peculiar Sense Organs in Diptera A great deal has been written concerning the dissemination of seeds and this topic constitutes one of the regular subjects for treatment in every text book of elementary botany, but the dissemination of fungi is rarely mentioned. Even the text-books on fungi or plant diseases give but an inadequate account of this phase of mycology. Observations and experiments show that fungi provide for the dissemination of their offspring and the perpetuation of the species in many and varied ways and in many cases with great effectiveness. It is undoubtedly true that the agricultural and commercial practices of our present civilization have very materially assisted nature in spreading broadcast numerous parasitic forms as well as countless numbers of harmless saprophytes. That fungus pests are more numerous now in this country than in former years is not imaginary, but a stern reality. It is true that with the rapid development of plant pathology during the last decade we have had diseases of plants brought to our attention more than ever before. The history of our agriculture shows that with the intercourse between nations, fungus pests have been fre quently transported from one country to another. It is my purpose to consider briefly some of the ways by which fungi, and especially those causing disease, have been and are being disseminated. HOW FUNGI ARE CARRIED In the first place brief reference may be made to the state in which fungi exist during their transport. They may be carried as spores, as sclerotia, or as mycelium. Most fungi produce from one to several different kinds of spores, or specialized reproductive bodies, which provide for the perpetuation of the species, just as seeds of our Spermatophytes provide for the production of more seed plants. Spores may be active, that is, motile or capable of locomotion, but in most cases they are not endowed with the power of movement; in the former case their own activity may carry them in an aqueous medium to points far away from the parent plant that produced them, but in the latter they must be transported by some outside agency. Spores are produced by fungi in enormous numbers. It is undoubtedly true that vast numbers of spores perish without ever finding suitable conditions for the production of new plants. It has been estimated for some species of mushrooms that only one spore out of twenty billion ever produce a new plant capable of spore production. Many contain a minimum of reserve food and become exhausted in their first attempt to establish themselves; some are not able to withstand adverse conditions, such as desiccation, low temperatures, etc.; certain types germinate at once without at resting period and thus frequently fail to reach a suitable substratum upon which to develop. Conidiospores may germinate at once and they are generally produced in much greater numbers than the more resistant ascospores which frequently require a resting period. Figures give but a slight conception of the enormous numbers of spores produced by fungi but they serve to emphasize their prodigality in spore production. It has been determined by careful analytic methods that a small "spore horn" or "tendril" of the chestnut blight fungus may contain as many as 115,000,000 pycnospores. Cobb states that a single head of smuted oats may contain as many as 500,000,000 spores, or a sufficient number to give 1000 per square |