1. What is flowering physiology？ 1-1. What is flowering？1-2. "Flowering" and "formation of flower bud" 1-3. Definition of the term "flowering" 2. Photoperiodic flowering 2-1. Critical dark length2-2. Night break2-3. Time measurement2-4. The sites of photoperiodic perception 2-5. Florigen 　　2-5-1. Grafting experiments suggesting the presence of florigen/2-5-2. Florigen may not be universal/2-5-3. Effect of florigen on stem elongation and flower formation/2-5-4. How long is florigen active?/2-5-5. Positive feed-back of florigen synthesis by florigen itself 3. Quest for florigen 3-1. Flower-inducing activity of salicylic acid3-2. Flower-inducing activity of phloem sap 3-3. Flower-inducing activity of water extracts of Lemna fronds 3-4. Florigenic activity of plant hormones 　　3-4-1. Gibberellins/3-4-2. Abscisic acid/3-4-3. Ethylene/3-4-4. Some chemicals other than plant hormones 3-5. Problems in bioassay3-6. Quest for florigen by physiochemical analyses3-7. Quest for florigen by techniques in molecular biology and molecular genetics 4. Alternatives to the florigen concept 4-1. Multiple factors 4-2. An inhibitor of flowering4-3. An electric signal 5. Molecular genetics of flowering 5-1. Mutants relating to change of vegetative meristem to flower meristem5-2. Flowering-time mutants 6. Vernalization 6-1. Vernalization and gibberellins6-2. Molecular genetics of vernalization 6-3. Vernalization and DNA demethylation 7. Stress-induced flowering