578 WHITE— STUDIES OF INHERITANCE IN PISUM. 



mutation. The pods on a single plant generally varied from pure 

 purple to purple streaked with green. Plants with all purple pods 

 also occurred. The seeds were either pure yellowish green, yellow- 

 ish green with purple flecks, purple with small yellowish green 

 flecks, or wholly purple. Seeds of all these colors occur together 

 on the same plant or even in the same pod or each type occurred 

 pure on single plants. Pedigree cultures for ten generations showed 

 that bud mutations or sports arose whereby pure strains were es- 

 tablished with yellowish green seeds. Other bud sports or muta- 

 tions gave rise to true breeding purple-podded strains. That these 

 were not the result of selection as is ordinarily understood by that 

 term is shown by their abrupt origin and their breeding true at once. 



Another mutation of the same type is the wild vetch-like 

 " rogue " which many varieties of cultivated peas throw in varying 

 percentages. Bateson and Pellew (5) have investigated the genetics 

 of this " rogue " mutation with the following results : The varieties 

 investigated were Ne Plus Ultra, Early Giant and Duke of Albany. 

 Thoroughly typical plants of these varieties occasionally throw 

 rogues and intermediate forms. The rogues, when fertile (rarely 

 sterile), have exclusively "rogue" offspring. The intermediates 

 from typical plants give a mixed progeny of a few typical plants 

 and many " rogues." Some varieties and some strains of the same 

 variety throw more " rogues " than others. Selected Gradus strains 

 throw about one per cent., while some varieties such as Fillbasket 

 appear never to throw rogues. Rogues crossed with rogues always 

 give rogues. 



These two cases of mutation appear to be similar to what Emer- 

 son (27.5) calls, in cases investigated by him in corn, "recurring 

 somatic variations," or what East (26.2, pp. 40-43) refers to as 

 recurring mutations, meaning of course that it is impossible to free 

 a variety from the recurrence of the mutation (in East's case, semi- 

 starchy seeds in varieties and segregate lines of sweet corn). 



If mutations are so rare in peas as our present knowledge seems 

 to indicate, how have all the numerous genetic differences among 

 them come about? In the absence of records, so far as can be 

 judged from what has been observed in other organisms, it is most 

 plausible to believe that most of the so-called factors originated as 



