CONTENTS 
PAGE 
Introduction . 5 
The Role of Sterility in Crop Production. 5 
Object of the Experiment. 6 
Sterility Among Dewberries and Blackberries. 6 
Varieties Tested: 
Dewberries . 6 
Blackberries . 6 
Method of Procedure . 6 
Results and Discussion . 8 
The Probable Causes of Sterility . 13 
Theories Advanced: 
1. Factor of Origin of Varieties . 13 
2. Structure of Flower, and Disease. (Double Blossom). 13 
3. The Daily Blooming Period of Varieties . 13 
4. The Amount of Pollen Produced by the Flowers. 13 
5. The Factor of Environment . 13 
6. Sterility Due to Hybridism . 13 
8. Natural Antipathy Between Pistils and Pollen of the Same 
Variety . 13 
Experimental Evidence as to the Cause of Sterility, and Discussion 13 
Pollinators for the Berry Plantation . 31 
Requirements for a Good Pollinator. 31 
1. Simultaneous Flowering Period . 31 
2. Abundance of Pollen . 33 
3. Self-Fertile Varieties . 33 
Self-Fertile vs. Self-Sterile Varieties to be Used as Pollinators for the 
Berry Plantation . 33 
Comparison of Fruits from Self-Fertilized vs. Cross-Fertilized Flowers.. 33 
Experimental Evidence . 33 
Results and Discussion . 35 
