Mutations 



83 



Many mutations among cultivated plants are the result 

 of continued selection for a period of years. This selection 

 assists in breaking the type and thus permits the mutation 

 to occur, and after the mutation has appeared, constant 

 selection is not necessary to keep the new variety pure. 



It has been stated that the peloric type of toad-flax 

 is of frequent occurrence in the wild state (Figs. 23 and 

 24). De Vries found its appearance even more common 

 under cultivation than when growing wild. He planted 

 the' seed of two toad-flax plants, one of which contained 

 a single peloric flower. Eighteen hundred plants were 

 obtained, of which seventeen, or nearly one per cent, 

 were wholly peloric. 



The snapdragon (Antirrhinum majus) is also known to 

 produce peloric flowers from time to time as mutations 

 (Fig. 25). Pelorics occur sometimes in Linaria dalmatica 

 and other species of Linaria; in fox-glove (Digitalis pur- 



FIG. 25. Antirrhinum majus: A, peloric flower from the middle of an 

 otherwise normal raceme ; B, normal flower of the same spike. 



