Mutations 



81 



mined whether they are the product of pure lines or not. 

 If they come from pure lines, in all probability they are 

 mutations ; if not, the new forms may be a result of hybridi- 

 zation, which may have taken place immediately preced- 

 ing the appearance of the anomaly or at a considerable 

 time previous to its appearance. 



New varieties and elementary species are seen to occur 

 more often under cultivation for three reasons : 



1. When new forms do occur, they are more likely to be 

 seen. 



2. Because of the relative lack of competition and hence 

 a better opportunity for preservation. 



3. The transfer of plants from the wild to the cultivated 

 state has a tendency to break the type and cause spon- 

 taneous new forms to ap- 

 pear. For this reason, 



we may expect a more 

 frequent occurrence of 

 mutations under culti- 

 vation. 



It is commonly ob- 

 served among gardeners 

 that so-called " sports" 

 are of very common oc- 

 currence. Some of these 

 are monstrosities which 

 are not inherited, but 

 many of them are mu- 

 tations and are inherited 

 true to type. The occurrence of double-flowered types 

 as mutations is common. 



B 



FIG. 23. A, B, Linaria vulgaris; C, 

 D, peloric flowers. 



