xiv Contents 



PAOKI 



apparently the rule Darwin's conclusions The need of 

 further work Experiments with self-sterility in pear 

 Self-sterility in other orchard trees Parthenogenesis 

 Xenia in corn Indications of xenia False xenia Other 

 secondary effects of pollination Parthenocarpic develop- 

 ment Parthenocarpic formation in pomaceous fruits 

 Seedlessness in the orange, grape, and banana Nonsexual 

 reproduction Thickened roots and tubers Cuttings 

 Precautions with cuttings Vegetative reproduction and 

 running out Relation of vegetation to fruiting Labora- 

 tory work References 347-380 



CHAPTER XV 

 THE SEED IN PLANT PRODUCTION 



Habitat conditions of the parent plant Localization of seed 

 production Maturity Conditions of harvesting and cur- 

 ing Duration of vitality Environmental conditions 

 Buried seed Delayed germination Effect of weight and 

 size of seed upon vigor Experiments with wheat Ex- 

 periments with cotton Experiments with tobacco Lab- 

 oratory or supplementary work References . . 381-399 



CHAPTER XVI 

 THE TEMPERATURE RELATION 



Climatic extremes and introduced plants Temperature and 

 production Cardinal temperatures Inhibition at high 

 temperatures Heat units Heat units and germination 

 The date-palm Control of temperature The temperature 

 of the plant Adjustment of structure Irritable response 

 Freezing Buds Laboratory work References . 400-414 



CHAPTER XVII 

 THE LIGHT RELATION 



The adjustment of plant members Light perception Diverse 

 requirements Light intensity Injurious effects Artifi- 



