136 Descendenz und Hybriden. 



Bateson, W., E. R. Saunders and R. C. Punnett, Further Experi- 

 ments on Inheritance in Sweet Peas and Stocks: Pre- 

 liminary Account. (Proc. roy. Soc. London. Ser. B. LXXVIl. 

 [1906.J 517. p. 236-238.) 



Later results have provided expressions which include many 

 of the peculiar phenomena of inheritance already witnessed in sweet 

 peas and Stocks. In sweet peas we have shown that purple may 

 occur, as a „reversion", from the cross between two whites, one 

 having long pollen grains, the other round. Simüarly in Stocks, 

 white glabrous X Cream glabrous gives „reversionary" Fi purple 

 hoary. (In both cases the parents are whites, i. e., free from sap- 

 colour, for cream is due to yeliow plastids, recessive to colourless 

 plastids.) 



The appearance of coloured flowers is due to the simultaneous 

 presence in the Zygote of two factors, belonging to distinct alleio- 

 morphic pairs, which may be spoken of as C, c, and R, r, the large 

 letter denoting presence, the small letter the absence of the parti- 

 cular factor. 



Hoariness of Stocks is similarly due to the coexistence of two 

 other factors, and the presence of either of these factors is also 

 allelomorphic to its absence. These two pairs are spoken of as H, 

 h, and K, k. But, though H and K may both be present, no hoari- 

 ness is produced unless C and R the colour-factors, are also both 

 present. For the actual development of hoariness four factors are 

 thus required. The existence of white-flowered hoary plants creates 

 a difficuity; but white ine a/ia is evidently a coloured form in reaüty, 

 for its flowers finge 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 Clements 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: 



Fl. 



1. Cream glabrous X Red or purple Red 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 Red or purple glabrous. 

 glabrous. glabrous. 



The truth of this account appears from the fact that in F.. 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 Fl' all the hoary plants coloured, and all the 

 glabrous plants white; while „white" (hoary) incana X sap-coloured 

 types gives in F- coloured hoary, coloured glabrous, and in addition 

 tinging „whites" in both classes. 



When a character is produced by the meeting of factors be- 

 longing to two distinct allelomorphic pairs, the Fa ratio will be 

 9:7 (i. e., 3+3+1), and consequently, when in sweet peas and 

 Stocks a coloured Fi is produced from two non-sap-coloured types, 

 the F2 ratio is 9 coloured: 7 white; but there are 4 gametically- 

 distinct types among the coloured and 5 among the whites. Most 

 of these have been now recognised experimentally. 



