VERNALIZATION of winter rye by chilling, which normally is carried out during the germination of ripe grain, has been successfully applied during ripening while the ears remained attached to the parent plant. To this end each ear was placed in a boiling tube inserted in the neck of a vacuum flask containing ice. Thus the ear was not in direct contact with the ice and a fairly even temperature of 1°–1·5° C. was maintained within the tube. The ears were selected for treatment at various times after anthesis, and, after being kept for twenty-four days at a low temperature, allowed to finish ripening normally. Ears which were selected from the middle period of ripening alone produced grain which on spring planting proved to be vernalized. The control grain came from ears kept for a similar period in vacuum flasks without ice.