MUTATION 63 



by the addition of at least a single character, while 

 varieties are regressive mutations distinguished from 

 the parent type by the loss of at least one character. 

 Both breed true to their respective modifications. 



These different concepts of what constitutes a 

 species, illustrated diagrammatically in Figure 31, 

 pave the way for a better understanding of muta- 

 tions in connection with heredity. 



6. Plant Mutations found in Nature 



The oldest known authenticated case of a plant 

 mutation is the often cited instance of the *' fringed 

 celandine," Chelidonium laciniatum, which made its 

 appearance in the garden of the Heidelberg apothe- 

 cary Sprengel in 1590 among plants of the "greater 

 celandine," Chelidonium majus. The fringed cel- 

 andine bred true at once and is now a widespread 

 and well-known species. 



The purple beech has appeared historically as a 

 mutant among ordinary beeches upon at least three 

 occasions in widely separated localities, and it has 

 always given rise to a constant progeny. 



The "Shirley poppy," notable for its remarkable 

 range of color, originated from a single plant of the 

 small red poppy, Papaver rhoeas, which is commonly 

 found in English cornfields. 



Instances are known of double flowers among 

 roses, azaleas, stocks, carnations, primroses, petunias, 

 etc., arising from single flowering plants, the seeds of 

 which in turn produce double flowers. 



