Mutations in Cultivation. 187 



It is clear that we can only advance by very small 

 steps dealing at each step v^ith a single mutation. But 

 even single mutations may be of enormous importance 

 in horticulture or agriculture. Much that now seems 

 unattainable may come within our power if only we can 

 obtain some insight into the fundamental principles in- 

 volved in mutation. There lies here a wide field of work 

 the results of which will be as important to the biologist 

 as to the practical man. 



§ 25. MUTATIONS IN CULTIVATION. 



In a preceding section {% 23) I endeavored to show 

 that man}^ of the elementary species which exist in a 

 state of cultivation had arisen before they were intro- 

 duced into it. But it does not follow that this is always 

 the case as Jordan, Kerner and others believe. 



On the contrary in many cases there is historical 

 evidence which at least makes it highly probable that 

 mutations occur in the garden and the field no less than 

 in the wild state. But it usually happens that the new 

 form is not seen until it is alreadv established; how, 

 when and where it arose cannot be discovered, or at 

 most only with a small degree of certainty. 



According to the theory of selection the origin of a 

 new form is a gradual process which we can observe 

 whilst it is taking place. But the evidence at our dis- 

 posal does not support this theory. It is true that forms 

 wdiich have arisen suddenly exhibit a high degree of 

 fluctuating variability and so give the selector the oppor- 

 tunity of intensifying the new character. But that is 

 a very different matter from the gradual origin of the 

 new character. 



