Peer review

A large number of substitution derivatives of coumarin were examined. In every case the activity was wholly or partially removed by substitution. A number of growth regulators of the 2:4-D type were examined. These acted as germination inhibitors, in some cases being more active than coumarin. It is concluded that the activity of coumarin as a germination inhibitor is due to its specific structure, consisting of an unsaturated lactone linked to an unsubstituted benzene nucleus. Any change in this structure leads to the partial destruction of the activity as a germination inhibitor.

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