C. Pellew and F. M. DrRHAM 181 



II. Occasionally hybrids of tlie form known as P. Kewensis are 

 obtained. These are of two kinds, one partially sterile, having the 

 diploid number 18 chromosomes, the haploid number 9 chromosomes, 

 the other fertile and having 36 and IS chnimosomes respectively. 



III. The hybrids whether maternal or otherwise are obtained in 

 very small numbers, and although F^ seed which appears good is often 

 formed, great difficulty in germinating it is met with. Uncertain 

 germination is however common in these plants. 



IV. P. Kewensis self-fertilized generally breeds true to type, segre- 

 gating only in certain factors such as degree of mealiness and flower 

 colour ; when crossed with parent types it commonly produces maternal 

 hybrids, but in rare cases gives evidence of segregation. 



V. The genetic behaviour of two plants of Kewensis, bred from 

 Kewensis [F^ Kewensis x florihundii], received from Messrs Veitch in 

 1911, was however peculiar. The offspring of these plants did not 

 resemble Kewensis, but approached nearer to fluribitnda. One of them 

 was found to have 18 diploid and i) haploid numbers of chromosomes, 

 and this plant exhibited segregation, giving new forms representing 

 recombinations of florihimda and verticiUata characters. These plants 

 are also peculiar in that their seed germinates freely. 



VI. Among these new forms are many shades of yellow not 

 previously known in these plants. When we began our work, the only 

 colours known were the full yellow of floribunda type and of Kewensis, 

 the paler yellow of verticiUata, and the pale cream yellow of the variety of 

 Jioribunda known as isabellina. The full yellow and the pale isabellina 

 shade evidently depend on a factorial difference, the full yellow being 

 a dominant. The numbers given have however a wide range of 

 irregularity. The factorial inter-relations of the new colours have not 

 yet been sufficiently investigated. 



VII. The diploid plant which thus exhibits segregation has also 

 been crossed successfully with Kewensis tetraploid. From this cross 

 plants intermediate between Jioribunda and Kewensis have arisen, and 

 also a few plants resembling ^ori6((/(f?((. 



