The germination of freshly harvested lettuce seeds can be promoted by placing them upon a very moist substratum or in water. When lettuce seeds are repeatedly placed in contact with the same medium there is a gradual reduction in the percentage of germination which indicates that growth-inhibiting metabolic products diffuse from the seeds into the substratum. The inhibiting substance appears to be associated with the reversion of lettuce seeds into secondary dormancy at high temps.