In 1868 Darwin published his book The variation of animals and plants under domestication (two volumes). In it nearly all animals bred by mankind and all cultivated plants are extensively discussed. For example the pigeons of which Darwin proved that they all are descendants of one wild species, the Rock Pigeon. In this book Darwin has used the huge quantity of information he had collected in the many years of correspondence with breeders and growers.

An example of a cultivated plant which is discussed in the book is maize. Darwin describes how the plant has been imported from America, where the Aztecs already made sugar out of it. Most of the wild ears of maize have 8 rows of grains, but sometimes ears with 10 grains in a row occur. When seeds of these are sown, the ears have 10 grains on average, but also ears with 12, 14 of even 16 grains are present. Cultivating further with these grains will give occasionally ears with 18 or 20 grains a row. Nowadays the ears have 22 grains. Of course the crop has increased very much in this way. The smaller plants in the illustration are still older ancestors of the maize.

Darwin 47

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