Abstract
1. Germination studies with Hypericum perforatum seed showed that tap water retards germination as contrasted with the germination rate in distilled water. Mixtures of the two containing as little as 10 per cent tap water cause as pronounced germination delay as pure tap water. A relatively short period in tap water, followed by transfer to distilled water, also results in a definite retardation. 2. High alkalinity of the tap water and its ionic constitution are both possible causes of the effect observed. The data show that it is not a question of alkalinity, for similar results can be produced in solutions at or below the neutral point. The effects of the various ions present in tap water indicate that calcium causes the retarded germination. 3. No conclusive explanation is offered as to the method of operation of calcium in delaying germination. The data suggest that it alters the permeability of the coat to water.
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