334 POPULAR SCIENCE MONTHLY. 



His aim will not be accomplished by one crossing. Connecting links 

 are required, and therefore the North American beach plum has to be 

 crossed with other American and Japanese plums (Prunus triflora and 

 P. Americana), and each of these hybrids with four or five kinds of the 

 common plum. Finally a series of hybrids is developed from which 

 almost anything can be expected. 



It is natural that by such crossing we must expect the appearance 

 of undesirable characters as well as desirable ones. Some plants pro- 

 duce only good, others only bad, characters, but the greater part exhibit 

 some good points in connection with a larger or smaller number of 

 undesirable qualities. From hundreds of thousands only those must be 

 selected which possess all the desired characters. To make this possible 

 it is necessary not only to cross six or eight kinds with one another, but 

 to use as many sub-species and varieties as possible for the experiments. 

 This work necessitates hundreds and even thousands of experiments. 

 The result of each crossing can only be judged by the fruit, and this 

 indicates new combinations. It can easily be seen what an immense 

 amount of work, patience and capacity of judgment and choice is re- 

 quired to reach the ultimate aim. Yet Burbank told us on that re- 

 markable evening of many such instances. He was enthusiastic in his 

 hope to be able to realize all this during his life. 



The making of hybrids from the different species of plums naturally 

 brought us to a subject which, for me. was of the greatest importance 

 from a scientific standpoint. As Arrhenius and Loeb also felt more 

 interest in the theoretical side of these problems, I took the first oppor- 

 tunity to bring the conversation to that point. 



I had in mind the ' pitless prune.' Just imagine this, reader ! 

 Next day Burbank took us to a plum tree heavily loaded with clear 

 blue, very attractive, yet small plums. He picked a few and asked us 

 to bite right through the middle of the fruit. We did as requested, 

 and although we knew there was no stone in the plum, we experienced 

 a feeling Of wonder and astonishment. Inside the plum was a seed, 

 like an almond in its shell, and with the taste of an almond, but 

 without the stony covering. When cutting through the fruit, we found 

 the seed surrounded by the green fruit-flesh, the innermost part of 

 which was a jelly-like mass, in which could yet be seen some remnants 

 of hard little stones, that scarcely offered any resistance to the knife. 

 Burbank declared, however, that he was not at all satisfied with the re- 

 sult, and said that he had already young trees with fruits, in which 

 nothing could be detected of the stone. 



Osterhout told us about the impression this plum made on Professor 

 Bailey, professor of agriculture at Cornell University. He came un- 

 prepared before this tree, and Burbank, always full of humor, thought 

 it a good opportunity to play a little trick. Bailey had declared that 



