THE GENUS ROSA 283 



Baker in his " Review " in 1864, and R, gracilcsceiis, R. Smifhii, 

 R. laevigata and R. occideiitaUs by the same worl<:er in the 

 Monograph in 1869. 



In none of these cases, save R. Wilsoni, was hybridity 

 suspected. That curious form, however, aroused suspicions 

 in the mind of Borrer, for in speaking of it he asks " Can it 

 be a hybrid product?" and foll,ows this with the remark, " Mr. 

 Wilson finds several bushes of it, which discourages sucli an 

 idea." 



Thus a fact that, after due examination by a competent 

 geneticist, would have strengthened his earlier suspicions 

 served to lull them with Borrer. Had the phenomenon of 

 heterosis been recognised tlien, the remarkable speed with 

 which these hybrid roses spread vegetatively, and in doing so 

 give rise to clumps independent of the parent bush, would 

 inevitably have directed attention to the fact that all the 

 Wilsoni bushes occurred along the Menai Strait, and radiated 

 from one centre. 



Once again Christ supplied the key to the derivation of 

 Rosa involuta and its satellites. By careful analyses of its 

 characters, coupled with other pertinent facts, he proved 

 beyond cavil that it had sprung from a crossing of Rosa 

 spinosissima and R. tomentosa {sens, laliss.) 



If we remember that in making these decisions the widest 

 view has been taken of Rosa canina regarding it as equivalent 

 to the Afzeliana. -\- EncanincB, and of R. tomentosa by looking 

 on it as including the Villoscc and Toinentosce, on the same 

 basis one more combination is possible, and that is Rosa 

 pinipinellifolia X R. rubiginosa. Precisely as in the other 

 two instances, roses of this parentage had actually been 

 encountered, Rosa biturigensis described by Boreau in 1857, 

 and R, involuta var. Mooreihy Baker in 1869. Moreover, the 

 relationship of the former plant had already been determined 

 in a fairly accurate sort of way, since Boreau terminates his 

 description with these words, " Looks like R. pinipinellifolia 

 but nearest rubiginosa in its characters, differing therefrom in 



