Severe injury was observed on white cedar and several species of pine adjacent to highways in southern Ontario in the spring of 1970. Foliar injury, measured quantitatively as the ratio of brown to total leaf tissue, and foliar levels of sodium and chloride higher than background levels occurred on trees up to 120 m from the highway, particularly on the downwind side of the highway, on the windward side of the tree, and on trees in exposed positions. Injury and foliar levels of sodium and chloride progressively declined at greater distances from the highway. For a given level of sodium or chloride more damage occurred on the windward side than on the sheltered side of the tree. The data suggest that salt applied to highways in the winter is whipped up in a spray by traffic, blown onto vegetation, and contributes to leaf injury. Wind and lower than average winter temperatures also appeared to contribute to the injury observed in 1970. At similar foliar concentrations of sodium and chloride white pine showed twice as much injury as white cedar. Of the pines close to the highway, damage was greatest on white pine and red pine, intermediate on Scots pine, and least on Austrian pine and Mugo pine. At similar levels of damage all pines contained similar foliar levels of sodium and chloride.

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I I ' 2.* clarify the fole that dilatation and shear play in heterogeneous yielding. Application of the above studies t o the mechanical properties of composite systems is also in progress under a grant from the National Institute of Dental Research. B. PolymerSolvent Interactions I ESimultaneous absorption and swelling measurements on various solid polymers immersed in active liquid environments have shown conclusively that the gravimetric technique commonly used for the determination of the cohesive energy density of polymers can give misleading results. These experiments have led to the design of a constant volume polymerliquid interaction cell which is now operational. Several crosslinked and non crosslinkedpolymers will be studied at constant volume in order to determine true cohesive energy density parameters. Also, the measurements may prove useful to a study of the disorder spectrum of amorphous materials.