1905.] Inheritance in Sweet Peas and Stocks. 



237 



form in reality, for its flowers tinge on fading, and its embryo has the deep- 

 green colour characteristic of purple varieties. Apart from breeding-tests, 

 however, white hoary Bromptons show no visible indication of colour, and as 

 yet they constitute a marked exception. 



White glabrous and cream glabrous types contain both H and K, the 

 two elements of hoariness. One of them contains C and the other contains 

 R All sap-coloured types studied contain one only of the two factors 

 H, K. Consequently, we find the following result, which formerly seemed 

 paradoxical : — 



*v 



1 . Cream glabrous x Eed or purple Eed or purple hoary. 



glabrous 



2. White glabrous x Ditto Purple hoary. 



3. Cream glabrous x White glabrous Ditto. 



4. Any red or purple x Any red or purple Eed or purple glabrous. 



glabrous. glabrous. 



The truth of this account appears from the fact that in F 2 from cream 

 glabrous x white glabrous all the coloured are hoary and all the whites are 

 glabrous. Again, purple (hoary) incana x cream glabrous gives in F 3 all the 

 hoary plants coloured, and all the glabrous plants white ; while " white " 

 (hoary) incana x sap-coloured types gives in F 2 coloured hoary, coloured 

 glabrous, and in addition tinging " whites " in both classes. 



When a character is produced by the meeting of factors belonging to two 

 distinct allelomorphic pairs, the F 2 ratio will be 9:7 (i.e., 3 + 3 + 1), and 

 consequently, when in sweet peas and stocks a coloured Fx is produced from 

 two non-sap-coloured types, the F 2 ratio is 9 coloured : 7 white ; but there 

 are 4 gametically-distiuct types among the coloured and 5 among the whites. 

 Most of these have been now recognised experimentally. 



When Fi is purple the coloured class consists of purples and reds. In 

 both sweet peas and stocks the ratio is 27 purple, 9 red, 28 white, composed 

 thus :— 



27:9:9:9:3:3:3:1 



v • 



28 



The purples are due to the presence of a " blue " factor B, allelomorphic 

 to h. its absence. Unless C and E are both present, B cannot be perceived 

 without breeding tests. The three pairs, C, c, E, r, B, b, by entering into 

 all possible combinations according to the simple Mendelian system, give the 

 results observed. 



This scheme takes no account of the sub-classes which sometimes occur 



