Contents -- Preface and Acknowledgments -- Part I - The Tree and the River -- 1. The Tree -- 2. The River -- 3. Regeneration -- 4. Water and Nutrient Relations -- 5. Perpetuate and Prolifeate -- Part II - Variation and Variability -- 6. Clones -- 7. Why Sex? -- 8. Password? -- 9. Natural Hybridization -- Part III - From Species to Populations to Genes -- 10. Common Gardens -- 11. Transplanted Trees -- 12. Getting Closer to the Genes -- 13. Migrant Trees -- 14. Adaptation and Its Limits -- Part IV - Trees and Society -- 15. Changing Rivers-Changing Landscapes -- 16. The Dawn of Agriculture -- 18. From Farmers' Trees to Tree Farms -- 19. Poplar-A Model Tree -- 20. Tree Genomics and Beyond -- 21. Between Old Growth and Plantations -- 17. The Farmer's Trees -- 23. Outlook -- 22. The Essence of Trees -- Notes -- Glossary -- Bibliography -- Index.