Plants have determined man's history and they will determine his future. Whether they were suspended in the primeval soup of the oceans, or more firmly anchored after their emergence onto land, plants modified the earth's early atmosphere, fixing carbon dioxide (CO2) and releasing oxygen (O2), making possible the evolution of primitive animal life and, much later, of man himself. Plants are at the base of every food chain, supplying us with both building and clothing materials, with wood for cooking and heating, and with fuels to generate power. Such green threads connect our most fundamental activities yet, despite this, we have until very recently taken plant growth and health for granted. Many aspects of plant physiology remain a mystery to us, particularly where they concern plants under the variable conditions of the field – away from the controlled conditions of the laboratory. Still in its infancy is the study of how the physiology of an individual plant is modified when it functions as a member of a community in a natural environment. One concern of the greatest current interest is the extent to which plants, with their capacity to fix CO2, might ameliorate changes in the composition of the earth's atmosphere that threaten our safe and familiar world.

Given the importance and urgency of the latter, it is salutary to review the progress we have made in our scientific understanding of plant growth and to reflect that our understanding began less than three centuries ago. And this is where the Darwin family comes in.

A strong green thread ran through that family, connecting different generations across two hundred years. Erasmus Darwin (1731–1802), his grandson, Charles (1809–82), and his great grandson, Francis (1848–1925), were all botanists of distinction, each fascinated by the movements of plants as they seek light, nutrients and water.

Mention of the name Darwin has for too long conjured an image of just one of them, Charles, his theory of evolution, fossils, struggles for survival in the animal world, and man's origins with the apes. As this book will reveal, the image is misleading where Charles in concerned.