xvi] Practical Application 299 



or less tinged with magenta, which evidently exhibit the 

 two gametic elements that must be combined in one zygote 

 in order to produce the Lavender. 



In this case the bright magenta-reds immediately breed 

 true when self- fertilised. In regard to the tinged whites 

 there is a complication which might repay further study *. 



There is another colour in Primula Sinensis which 

 apparently cannot exist in a pure form. This is a peculiar 

 shade of " crushed strawberry," and the two pure forms by 

 the union of which it is formed are the deep crimson of 

 "Crimson King," and the white with a bright pink eye 

 brought out by Messrs Sutton under the name " Duchess." 

 By crossing these two together, the peculiar heterozygous 

 colour can at once be produced. 



But though such examples are not rare, they are in a 

 minority, and speaking generally we may feel fairly con- 

 fident that a given type can be made to breed true, and 

 to perpetuate its good qualities indefinitely. A doubt 

 should perhaps be expressed as to the possibility of fixing 

 permanently such a property as a high degree of fertility. 

 Respecting the transmission of that character and the con- 

 ditions governing its existence little is positively known, and 

 to discuss the various indications properly is not possible 

 within present limits ; the remark must suffice that the 

 evidence on the whole suggests that hopes of fixing per- 

 manently such a quality as excessive egg-production of 



* When such tinged whites are self-fertilised, most of them are found 

 to breed true. Some, however, in addition to their own type throw some 

 lavenders, and occasionally even a magenta-red. This result has occurred 

 both at Messrs Button's and also in the sowings which Mr R. P. Gregory 

 and I have made. The fact is probably due to imperfect classification of 

 the lavenders and tinged whites. These shades of colour are liable to vary 

 somewhat, especially with temperature, colder temperatures causing more, 

 higher temperatures less colour in the flowers. From our general experience 

 of Primula colours we may feel assured that the white of the tinged whites 

 in this case is due to the presence of some dominant inhibiting factor, 

 which we may call D. The factor for colour, C, is common to all these 

 plants. The bright magentas are CCdd, the lavenders are CCDd, and 

 the tinged whites are CCDD. In all probability there is an irregularity in 

 the dominance of D, for which we cannot at present account, such that a 

 lavender may occasionally be so pale in tint as to pass for a tinged white. 

 Further analysis would doubtless show that the number of these dubious 

 plants is in fact definite, and possibly that their abnormal behaviour is due 

 to the possession of some distinct element. 



