principle that only combinations, but no primary characteristics, were produced. Only in one instance I encountered what seemed to be an absolute exception to this rule. It was an announcement of Lemoine of Nancy, the most celebrated breeder of garden novelties in France. He claimed that he had been able to produce by crossing double lilacs. Double flowers remain longer on the branches than the single, which usually drop off after a few days. To find out how it was possible to develop by crossing from single lilacs new varieties with entirely new characteristics I visited Lemoine in Nancy. Walking through his gardens. I put the question to him and received the following answer:
"That is very simple. As a boy I had seen in the garden of an old relative a specimen of Syringa azurca, a very rare lilac of an ancient type with double flowers. Remembering this, I bought that tree from the person who owned my relative's home. With this tree I crossed all varieties of single lilacs I had and got the double variety." Here we find again the same procedure: first buying, then crossing, later grafting or budding on other forms, but no creation of an absolutely new character. The number of combinations may be unlimited, yet the creation of new prime characters is entirely excluded.
This principle came into full evidence while we were in Burbank's grounds. He demonstrated to us 'white blackberries' with large fruit of a delicious flavor, which now are an article of commerce. I asked him about the origin of this crossing. Burbank explained that here and there in California occurred a wild blackberry with white fruit. He had crossed this plant with other forms. A white variety of the common raspberry has similarly been known in Eurpoe since olden times.
Another striking example is furnished by the spineless cactus, one of the novelties of which Burbank expects much. It is one of the Opuntias, a desert plant, the fruit of which is eaten and known as Indian figs. Its stem consists of big, flat slabs, joined together in the most fantastic manner. It reaches a height of six feet, spreading widely and growing luxuriantly. The fruit is much relished by cattle, as it is juicy, rich in foodstuff and has but few thorns. The whole plant is eaten by animals only when they are driven to do so by hunger, as it is covered with hard prickly thorns. If the plant is cooked for some time the thorns soften and the cactus becomes a nutritious food. This process of cooking is, however, too expensive for practical purposes, and hence a cactus without thorns would transform a barren desert into rich pastures. To reach this Burbank brought together wild Opuntias from Mexico, South Africa and various other countries as well as the commonly cultivated species. Among the specimens Burbank received, one was accidentally found without prickles on the Leaves and another with no thorns on the young shoots. It was, there-
