THE GENETIC BEHAVIOUR OF THE HYBRID 

 PRIMULA KEWENSIS, AND ITS ALLIES. 



By CAROLINE PELLEW and FLORENCE M. DURHAM. 



{Tlie John Iinu'n Horticultural Institution.) 



Introdtjction. 



The first Primula Kewensis was found growing among plants of 

 P. florihuada, and was thought to be an accidental hybrid of flwi- 

 bunda x verticillata. After a period of sterility it gave rise to a 

 perfectly fertile form of larger size widely known as a greenhouse 

 plant, and it is to this form that the name P. Kewensis is generally 

 applied. 



Inasmuch as the fertile Kewensis, though of hybrid origin, breeds 

 in general true, throwing at all events no plants like Jioribunda or 

 verticillata, a definite jiroblem is thus created, and our object was to 

 investigate this case of absence of segregation. 



The fertile Kewensis was moreover shown by Miss Digby to be a 

 tetraploid form having double the number of chn)mosomes posse.ssed 

 by verticillata or Jioribunda or the original hybrid, and we hoped also 

 to investigate the genetics of this condition. This part of the investi- 

 gation remains however incomplete, and will be the subject of a later 

 paper. 



Our experiments have consisted in breeding the various forms 

 on a considerable scale, and in making all po.ssible cross-fertilizations 

 between them. As regards the results of self-fertilization, in our 

 experience the species breed true except that florihunda throws a 

 definite pale-flowered recessive, called isabellina. The tetraploid 

 Kewensis breeds true approximately, the only evident segregation 

 being in regard to mealiness of the foliar parts. This is a recessive 

 condition but it appears in numerous intergrading states, the inter- 

 relations of which have not been successfully analysed. 



