84 CROSSING. 



it seems to us, is where some knowledge of Genetics is useful 

 for the practicians. 



But the further we progress, the more evident does it become 

 that the average horticulturist who is working to produce 

 new species of plants, and to ameliorate existing species, is very 

 much nearer the truth with his ideas about variability and its 

 causes than the average genetician. A very striking instance of 

 this fact can be seen in the attitude of the horticulturists to- 

 ward de Vries' mutation-theory. When de Vries revived the 

 idea that new species sprang into existence spontaneously, 

 without ascertainable cause, the horticulturists slowly began 

 to see mutations. Or rather, and this is significant, they began 

 to write in terms of mutability and to speak of mutations, 

 they began to use the terminology of de Vries. At the same time 

 they applied this terminology wrongly, they simply substitu- 

 ted the new fashionable term for "novelty" or for "new spe- 

 cies", without changing their ideas about the origin of these 

 novelties in the least. Whenever a horticulturist by means of 

 judicious advertising, flattery and auto-suggestion is made to 

 believe himself a great man, he may branch out into science, 

 and begin to give his real opinions based upon facts observed 

 instead of the latest fashionable theories. When Mr. Burbank, 

 a typical horticulturist of the old school in California, was visi- 

 ted by de Vries, the latter was able to make Mr. Burbank talk 

 and write about mutations. But when a little later Mr. Burbank 

 was made into "a famous scientist", he began to write books 

 for himself. Being thoroughly convinced of the fact that the 

 variability in his plants, enabling him to make his selections, in 

 the way in which all horticulturists have been working through 

 the last centuries, was caused, not by sheer good luck and 

 spontaneously, but as the result of appropiate crosses made by 

 Mr. Burbank himself, he nevertheless for a time retained the 

 term "mutation" then in vogue. He simply stated, that by 

 crossing species he produced "mutations". What he meant is 

 simply, that by crossing he obtained plants with new qualities, 

 not merely recombinations of existing ones. 



