a stoneless plum was entirely an impossibility, something that was outside of one human lifetime; he refused to believe the statement and could not be induced to risk his teeth on the experiment. To the great amusement of Burbank and Osterhout, he took a knife from his pocket, commenced to peel the plum and to cut away the fleshy part, in order to expose the stone, which he was sure would be there. How great was his astonishment when he finally did not find anything but the naked eatable kernel!
A couple of years ago when I read in one of Burbank's price lists about a stoneless plum, I shared a similar astonishment. How was it possible to bring about such a great change? Hybrids do not present, as a rule, any new simple qualities, only new combinations of already existing properties. The evident properties are often developed from more than one factor, and such composite characters may thus appear, without any new essential factors having been present. This is a fundamental principle in crossing, whether it is done for scientific or for practical purposes. But although the elimination of the stone is only a loss and not a gain of a character, such a loss is just as much outside the sphere of hybrid making.
My astonishment was, therefore, as great as that of Bailey, and I had long ago made up my mind to ask Burbank, if I ever had the opportunity, what secret method or what happy coincidence had enabled him to effect such a fundamental change in a plant. I put my question to him that evening, convinced that on the answer depended largely the scientific value of our visit. And for the second time I was surprised over the unexpected and simple reply: "About two centuries ago they knew in France a 'prune sans noyau' and I bought the fruit and raised a plant in order to cross it with others of my prunes." Thus there is no exception to the rule, there has been no real production of a new character, but we have only had a case of the general American principle: 'try everything.' Over the whole world Burbank looks for different kinds and varieties of prunes, no matter how insignificant they may be, however wild and uneatable, as long as they possess only one or another characteristic, which, in combination with the common kinds, may bring out a new variety of greater value.
To Professor Loeb and myself this was, to a certain degree, a disappointment. We had expected to learn a great deal about this point, the fundamental idea, if not the ultimate aim, of the studies of both of us—that is, the question of the nature and origin of new characters. We now surmised that Burbank's experience did not throw any light on this question.
I had before experienced a similar disappointment. About twenty years ago I was occupied with experiments on hybridization for horticultural purposes. I had already found at that time the general
