THE WASTING DISEASE OF ZOSTERA MARINA I. A PHYTOLOGICAL INVESTIGATION OF THE DISEASED PLANT

At the time that this study was begun, mid-summer, 1933, an epidemic, wasting disease had almost entirely destroyed the normally dense beds of the common marine eel-grass, Zostera marina, along the Atlantic coasts of North America and Europe. Since the plant is a prominent member of the shallow water community, sheltering a variety of larval and small sea animals, serving substantially as food for migratory game birds, and checking erosion of the bottom, and because the leaves are used for packing, upholstering, insulating, and other commercial purposes for which they are often peculiarly de sirable, the disappearance of the eel-grass became a problem of prac tical concern. It was recognized, too, that the extensive and persistent wasting of Zostera might indicatephytopathological relationshipsin the sea as significant as the more evident conditions in land vegetation. A further impetus was given this investigation by the popularization of a number of physical and chemical hypotheses for the depletion, of restricted application, and usually of a prejudicial nature. In France,Holland,Denmark, and Canada investigations were already in progress (6), (7), (11), (13), (18). The history of the disease here and abroad, the current condition of the eel-grass beds, and the economic and ecological implications of the wasting have been developed by a number of observers, and comprehensive summaries have been published from time to time by the U. S. Bureau of Bio logical Survey and others (1), (3), (6), (7), (10), (14). This paper is an account of investigations upon the pathology of the diseased eel-grass and upon the specific parasitic nature of an unidentified Labyrinthula, an amoeba-like organism with mycetozoan affinities, found in the leaves of the plant over the entire range @f the epidemic condition. They were begun in the attempt to extend the findings of Messrs. Fischer-Piette, Heim, and Lami of France,