160 Genetic Behaviotir of the Hybrid Primula Kewensis 



We find the consequence of crossing between any two of the forms 

 is that ahnost always the resulting offspring exactly reproduce the 

 maternal form, shou'ing no paternal influence. 



In such a case the obvious suggestion is that we have to deal either 

 with actual parthenogenesis or with the phenomenon denoted by the 

 term monolepsis, a condition, that is to say, in which the ovules need 

 the stimulus of fertilization for their development, though they take 

 no genetic contribution from the pollen grains. Under most stringent 

 tests positive evidence of true parthenogenesis has been obtained ; but 

 in view of all the facts we incline to suppose that the ovules are such 

 that while they can occasionally develop without fertilization they 

 more commonly develop in consequence of that stimulus. 



The offspring of the tetraploid Kewensis both on selfing and crossing 

 being simply a reproduction of the maternal type, no fresh recombi- 

 nations can in general be made, but perhaps the most interesting part 

 of our evidence relates to the production of a single diploid individual 

 from Kewensis which, in striking contrast to the behaviour of the 

 tetraploid, has exhibited segregation of an almost normal kind. 



The plant in question was raised from the self-fertilization of a 

 Kewensis which had been itself raised by fertilizing Kewensis with 

 florihunda. Among its offspring are various new colours and com- 

 binations of characters unlike any that have appeared before in 

 cultivation. Owing to intergradation it has not been found possible 

 hitherto to make a quite satisfactory or complete factorial analysis 

 of these types, though their genetic nature and properties are now 

 fairly clear. 



An interesting feature of these experiments lies in the fact that 

 the parent species dealt \vith differ in respect of the Moral dimorphism 

 characteristic of the Primulaceas. Whereas Jlorihunda is heterostyle, 

 verticillata is monomorphic, a condition only found in about five species 

 of Primulacese. 



The story of the origin of P. Kewensis is now well known to 

 horticulturists. It appeared at Kew in 1900, among plants of 

 P. floribunda, and was then thought to be a hybrid between 

 P. florihunda and P. verticillata. and this was subsequently proved 

 to be the case. According to the story often repeated in horticultural 

 journals, the first hybrids obtained were sterile. The plant was 

 described and figured in the Gardeners' Chronicle, 1900, jjp. 130 and 

 195. From this drawing we presume that the anthers were in the 



