Dormancy in Fruits of Fraxinus excelsior L.

The germination requirements of Fraxinus excelsior, the Europeanash, were determined as a preliminary stage to an investigationof the growth-substance content of dormant and germinating fruits.The embryo grows in size within the imbibed fruit before germinationcan take place and this growth is delayed through the firstwinter by the presence of an indehiscent pericarp which is impermeableto oxygen. Even when fully grown, the embryo is dormant andcompletes its chilling requirement during the second winter,after which a normal seedling can be produced.