3. White seedling classification. White seedlings can be classified satisfactorily soon after the seeds have germinated if they are germinated in the lignt. We use an old glass incubator for a germinator and keep the temperature about 75°F. Seeds are sterilized for 1 minute in a 1% solution of Hg Cl₂ and put in petri dishes, 100 to a dish. Under these conditions chlorophyll develops rapidly and classification can usually be completed within a week after planting.