ance of occasional spots, barren of vegetation, and incrusted with a white, red or yellow salt, which are to be seen at various points in Montana. These are the so-called " alkali" soils, and represent the worst phase of the condition. white " and the " black," the former consisting mainly of sodium sulphate and the latter of sodium carbonate. A solution of the "black" alkali, on account of its solvent action upon organic matter, dissolves the humus from the soil, and upon evaporation leaves it as a shiny black coating upon the surface, or in black concentric rings around the pools in which it collects. Vegetation is destroyed by contact with solutions of sodium carbonate, the stems, especially at the surface of the ground, being frequently completely girdled. Hilgard has found that as little as one-tenth per cent. sodium carbonate in the surface foot is deleterious. On the other hand a much larger amount of the "white" alkali may exist without affecting vegetation injuriously. I n Montana, the alkali consists almost entirely of sulphates and rarely possesses a strong alkaline reaction. I have found crops thriving in the presence of as much as six-tenths per cent. of the "white" alkali. The "white" alkali seems to produce its injurious effects when present in excess, not through any chemical influence, but rather by interference with the process of

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