The Effects of Cross and Self Fertilisation in the Vegetable Kingdom

What it is

This is a book by Charles Darwin, published in 1876. It reports years of controlled breeding experiments on more than sixty plant species, comparing offspring produced by cross-fertilisation with offspring produced by self-fertilisation.

Why it matters

Darwin had argued in On the Origin of Species that constant self-fertilisation could not continue forever in plants. This book provided the detailed experimental evidence for that claim, showing that inbred plants were usually weaker. The book became a founding work in the study of inbreeding, still cited by scientists today, and reveals Darwin's patient, decades-long method of testing his ideas through careful measurement.

Look closer

• Why might Darwin have needed to test so many different species before publishing his conclusions?
• What does the long list of experiments tell you about how scientific evidence is built up?
• Why might this subject have had personal meaning for Darwin, who was concerned about his own family's intermarriage?