552 WHITE— STUDIES OF INHERITANCE IN PISUM. 



pink, and reddish purple. The wild forms of Pisum most closely 

 related to our common cultivated forms all have colored flowers of 

 the reddish purple class. This last class is the only one in which 

 the color varies according to the variety. The degree of variation 

 is small and largely confined to a small group of wild or near wild 

 Asiatic varieties of which P. hiimile Boiss. and P. humile ? of Sut- 

 ton (74) are wild types. In this group of purple-flowered forms, 

 the colors are dull and of about the same shade in both standards 

 and other parts of the flower, the common purple-flowered forms 

 being bi-colored {i. e., lighter color shades in the standards). Ben- 

 ton is the most pronounced in light-colored standards of any of the 

 bi-colored purple-flowered sorts. Environmental changes commonly 

 met with in pea cultures have very little modifying effect on flower 

 color, though wet, cloudy weather causes pink-flowered plants to 

 produce white flowers. 



Varieties Studied. 



A large number of varieties have been studied, many of which are 

 designated under the sections devoted to leaf axil and seed coat 

 color. Reddish purple and white-flowered varieties are most com- 

 monly cultivated. The pink-flowered variety most easily procured 

 is " Irish Mummy," known also as Mummy, Egyptian Mummy, P. 

 sat. lunhellatum, etc. Many field peas and " sugar pod " peas have 

 colored flowers while the great majority of the garden peas are 

 white-flowered. 



Results from Crossing. 



Lock (56) and especially Tschermak (84, 86) have given ad- 

 mirable summaries of the work on this set of characters, making it 

 unnecessary to go into great detail here. 



Purple flower X purple flower gives only purple-flowered off- 

 spring in Fj and succeeding generations. 



Purple flozver X pink flower in F^ gives all purple-flowered off- 

 spring, which in F2 give both purple- and pink-flowered segregates 

 in proportions approximating the 3 : i ratio. In F3, the pinks and 

 part of the purples breed true, the remainder again breaking up in 

 the expected Mendelian proportions. 



