104 Varietäten, Descendenz, Hybriden. 



from the Zygote gives rise to a true albino bearing pure white 

 flowers and incapable of producing any pigment, though it may 

 carry either the ox3^dase or the modifying ferment, or both. 



The oxidation of the chromogen by the oxydase takes place in 

 two stages and is due to two factors, one producing only a tinge 

 of colour, whereas the second, a concentration factor, intensifies this 

 to the füll colour. The second factor cannot show unless the tingeing 

 factor is also present. 



The production of colour in the corolla tube must be represented 

 by a factor inherited independently of the factor which represents 

 colour in the lips. There is between these two factors a relation such 

 that colour only shows in the tube if the same colour is present in 

 the lips. On the other band the oxydase may be absent from the 

 tube but present in the lips, this condition giving rise to the delila 

 varieties. 



The yellow chromogen has not been found to occur in the tube 

 (except locally); hence the tube is never yellow, and in the crimson 

 varieties the tube is magenta, of an intensity corresponding with 

 the intensity of the crimson in the lips. 



In some cases the concentration factor occurs locally in streaks 

 and gives rise to striped forms. Striping is recessive to the unstriped 

 condition of the concentration factor, but is dominant to the tingeing 

 factor; zygotes homozygous in the striping factor show magenta 

 stripes on an ivory ground, while those heterozygous for the striping 

 factor show stripings on a tinged ground. Every striped magenta 

 has its delila form, and, in addition, its counterpart in the crimson 

 series. The anomaly recorded by de Vries has been encountered 

 again, namely, that striped forms throw some self-coloured offspring 

 in proportions not as yet determined. 



It appears then that the flower-colour in Antirrhinuni is deter- 

 mined by at least six Mendelian factors, the presence, absence 

 and combinations of which give rise to the numerous horticultural 

 varieties. In addition the carmine pink of the "Rose Dore" variety 

 is representable by a factor which depends for its manifestation on 

 the presence of the yellow or ivory chromogen. In the presence 

 of intermediate magenta or crimson it gives a still deeper type, deep 

 magenta or crimson. 



A variety known commercially as "White Queen" was mentioned 

 in the author's earlier paper upon Antirrhinuni (Roy. Soc. Proc, B, 

 vol. 79, 1907). This form appeared to be a white with yellow pigment 

 on the palate and in the hairs in the tube. Apart from the yellow 

 patch on the palate it is indistinguishable from the true albino, but 

 when mated with albinos and yellows it revealed itself to be an 

 ivory, and in F^ a yellow was extracted rather paler in colour than 

 the yellow used in the other matings. This paler yellow, of which 

 "White Queen" is the ivory type, gives, when the other factors are 

 added, a series perfectly comparable with that from the deeper 

 yellow, but differing in that all the varieties are a shade paler, due 

 to the paler fundamental yellow. The paler is dominant to the deeper 

 yellow when the two are mated together. 



The author gives details of the matings and the offspring pro- 

 duced (which number about sixteen thousand plants) in a series of 

 tables. R. P. Gregory. 



Wheldale, M. Note on the Physiological Interpretation of 



