No. 597] INHERITANCE STUDIES IN PI SUM 



535 



The Pigments of Cotyledon Color in Pisum 

 Bunyard (see Darbishire, p. 131) has shown that both 

 yellow and green cotyledon varieties have a yellow and a 

 green pigment in their cotyledons when the seed is im- 

 mature, but the yellow cotyledon varieties possess a fac- 

 tor (an enzyme perhaps), which causes the green pigment 

 to fade on the maturity of their seeds. Thus green pig- 

 ment is epistatic to yellow pigment, since, when both are 

 present, only the green is in evidence. 



The Genetics of Cotyledon Color in Pisum 

 Historical 



As early as 1729, according to Darwin (1876, 1, p. 428) 

 white (yellow cotyledon) and blue (green cotyledon) peas 

 were found in the same pod and these results were under- 

 stood to be due to chance crossing. Wiegmann, Goss 

 (1824) and others observed that varieties of Pisum breed- 

 ing true to blue peas when crossed with pollen from vari- 

 eties breeding true to white peas, always showed a direet 

 and immediate effect of the pollen parent. Gartner 

 (1849) and later hybridists incorrectly regarded this 

 phenomenon as xenia, believing that tissues of the parent 

 generation were affected so that the color of the seed was 

 changed. The fact that the change in color was due to an 

 embryonic character of a new hybrid generation seems 

 never to have occurred to them. The true significance of 

 these facts were never understood by Knight, Goss, Gart- 

 ner, nor any of the hybridizers before Mendel's time. 

 Knight distinguished between cotyledon colors and seed 

 coat colors, and Goss and others had observed practically 

 everything regarding crosses between green cotyledon 

 and yellow cotyledon peas except the numerical propor- 

 tion of one to the other in the F 2 generation. Darwin 

 (1876, p. 348) mentions some observations of Masters, 

 which, if authenticated, show a complex state of affairs 

 in the inheritance of cotyledon color, since Masters claims 

 to have obtained both yellow (white) and green (blue) 



