Collapse of the Seed following the Mating of Hordeum JubatumxSecale Cereale.

the endosperm as a storage tissue and the large size of the normal caryopsis. Cytogeneticists interested in the cereals were early impressed, accordingly, with the importance of this stage in the life cycle of the plant for the general problem of hybrid incompatibility. It is not surprising to find, therefme, that a larger amount of work has been directed toward discovering the basis of hybrid seed failure in these plants than in any other group of angiosperms. Some of the histological findings on the Gramineae as put forward in their original form, however, are seemingly a t variance with more recent evidence on seed collapse as manifested in certain Dicotyledons. Additional data are desirable, therefore, on the question whether seed failure following hybridization of distantly related forms follows a common basic pattern or differs significantly from group to group. T is readily observable in cereal species hybrids because of the persistence of