WHITE— STUDIES OF INHERITANCE IN PISUM. 577 



of P. humile Boiss. (Sutton, 74) and various varieties of P. arvense 

 and P. sativum. Sutton made 40 crosses, using in each case P. 

 humile as one parent and 10 varieties of white-flowered {P. sat.) 

 and 7 of colored {P. arv.) as the other parents. The results were 

 various, but apparently each combination produced seed. When 

 planted some failed to germinate or died immediately after germina- 

 tion, others reached the flowering stage but no seed were produced 

 and still others produced seed, which failed to germinate. In a few 

 cases, the F^ seed germinated, and the plants flowered but no seed 

 resulted. In four cases, the F^ plants were completely fertile, two 

 of the hybrids having white-flowered P. sativum ancestry and 2 

 having colored-flowered P. arvense ancestry. 



In crosses involving this same form (the seed of which Mr. Arthur 

 Sutton kindly sent me) and forms of P. elatius, P. sativum and P. 

 arvense, the writer obtained plants completely fertile in F^. In the 

 crosses, however, great difficulty was experienced in making them 

 "stick," and the majority of cross pollinations resulted in failure. 

 Many of the F^ generation seed failed to germinate, though only 

 plump seed were planted. 



Mutation. 



As compared with such organisms as the pomace or fruit fly, 

 Drosophila mutations are very rare in peas. All horticulturists and 

 breeders remark on the extreme constancy of pea varieties, some 

 of which have been in existence for at least a quarter of a century 

 without showing any striking modifications, and one variety, the 

 British Queen, is said by Sherwood to be practically a century old. 

 Several of the varieties mentioned by Darwin (22), such as Victoria 

 Marrow, Pois geant sans parchemin, Scimitar, Auvergne, Champion 

 of England, are still in existence to-day and very little changed, so 

 far as one may decide by the descriptions written in his day. Tedin 

 {yy) who has made detailed studies of a large number of varieties 

 at Svalof and who is on a special lookout for mutations has found 

 them rare and none of them of much practical value. 



Fruwirth (34) in conducting selection experiments on a variety 

 of pea with pods and seeds varying in all degrees in the amount of 

 purple pigment it possesses, discovered a very curious type of bud 



