524 WHITE— STUDIES OF INHERITANCE IN PISUM. 



Heterozygous yellows or F^'s X the green-seeded parent gave a 

 ratio of i yellow : i green as follows : 



Mendel, 104 yellow : 104 green, 



Tschermak, loi yellow : 100 green. 



As regards the F„ generation from green X Goldkonig yellow, 

 the data are as yet very scant. White (98), however, from an F, 

 progeny of 14 crosses found 253 seeds had green cotyledons and 

 74 had yellow or yellowish with slight green tinge, the proportions 

 approximating 3 green : i yellow or just the reverse of the common 

 result. No F3 generation data are as yet available. All green and 

 yellow cotyledon varieties used in crosses with Goldkonig crossed 

 with each other gave the usual 3 yellow : i green ratio. 



In applying Mendel's law to data such as the above, one must 

 always bear in mind, as pointed out recently by Pearl, that Mendel- 

 ism is essentially a statistical method and the law a statistical de- 

 duction, requiring large numbers and dealing only in averages. The 

 danger of drawing conclusions from small numbers is well shown 

 in a survey of the extreme variation in Fo ratios derived from 

 single Fi plants. 



For example, the greatest variation in 



Mendel's records (60) was 32 Y : i G and 20 Y : 19 G, 



Bateson's records (i) was 60 Y:9 G and 2^ Y:20 G, 



Corren's records (14) was 92.3 per cent. Y:'/.'/ per cent. G and 



55.8 per cent. Y:44.2 per cent. G, 

 Lock's records (54) was 14 Y: i G and 7 Y:8 G. 



Bateson (i) conducted experimental inquiries to determine the 

 significance of these fluctuations, but found them to be purely 

 fortuitous, as did Mendel (60) before him. 



Interpretation. 



In the light of the above data the hereditary differences between 

 yellow cotyledon and green cotyledon varieties of peas may be desig- 

 nated by G and I. G represents the hereditary determining sub- 

 stances or factor for green pigment, while I is a factor or deter- 

 miner which causes the green pigment to disappear when the seed 



