BURBAXK'S HORTICULTURAL NOVELTIES 223 



them is greater than in small cultures. In small private 

 gardens they are very rare, but in large nurseries they will 

 hardly ever fail, although they may often be much rarer than, 

 for example, one in a year. 



Hybridizing being one of the most important proce- 

 dures in many of the larger nurseries, the question has often 

 been raised whether such chance seedlings should be more 

 frequent, or rarer, after crossing than in pure strains. Of 

 course, this question is of the highest practical as well as 

 scientific interest, because if it had to be answered in the 

 affirmative, at least one possible cause would be indicated. 

 It seems quite possible that such should be the case, and 

 even our knowledge concerning the numerical laws of the 

 splitting of a hybrid progeny does not exclude the possibility 

 that among a thousand and more offspring some chance 

 deviation may occur. As yet, however, the evidence at 

 hand is too rare to justify a definite conclusion. 



In this respect the same conditions prevail on Burbank's 

 farms as everywhere else. Of course, sports occur quite 

 often and, in many cases, may even be produced at will. But 

 sports include a wider range of variability than the chance 

 seedlings. The latter can always be considered as sports, 

 but not all sports belong to this same group. A critical 

 review of some of the most interesting sports among the cul- 

 tures of Santa Rosa and Sebastopol will best prove this, and 

 at the same time it will give an opportunity to convey a still 

 clearer idea of the bearing of Burbank's methods and results 

 on the science of evolution. 



In the first place, the occurrence of elementary species 

 in nature often opens definite possibilities for culture and 

 selection. Burbank showed me a highly interesting sport 

 of a Mahaleb cherry or Prunus Mahaleb. It grew in a little 

 grove of shrubs of the same species, on his Sebastopol farm. 

 It had yellow berries instead of black ones and showed some 



