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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- 



