As one of the mechanisms of self-incompatibility in the flowering plants, certain cases are known in which the germination of pollen is decreased. This category includes some species of the Orchidaceæ, Lilium, Secale, Linum, Passiflora, Malus, Prunus, Melilotus, Pelargonium, and several species of the Cruciferæ etc. In the Cruciferæ CORRENS(1913) observed this fact in Cardamine pratensis, RILEY (1936) in Capsella grandiflora, STOUT (1931) in Brassica pekinensis, and SEARS (1937) in Brassica oleracea and Raphanus sativus. This may be true of the family in general.