254 E)R- J- W. HESLOP HARRISON ON 



a close resemblance. Even then I was sceptical as to the 

 RubiginoscB showing to the full the capabilities of the other 

 sections, so much was I influenced by the uniformity of the 

 full green R. rubiginosa growing sporadically in a sub- 

 spontaneous way in our hedges. I simply couldn't imagine 

 its yielding glaucous leaved varieties. This last stumbling 

 block was likewise removed by Traaen. Thanks to him, I 

 now have a splendid series both of the glabrous and of the 

 hairy pruinose Rosa glauci-rubiginosa. and R. supra-rubiginosa, 

 whence we see that R. rubiginosa can also produce all four 

 minor forms described below. 



In this fashion the facts which were destined to give rise 

 to, and then impress, the idea that species formation in the 

 RoscB was on an orthogenetic foundation were accumulated.* 

 We are now in a position to expand and systematise the 

 notion. 



Whatever the common ancestor of the Canince was, it 

 appears, if one judges from its geographical distribution, to 

 have separated early into three divisions, each of which in 

 turn gave rise to two allied sections, the pairs being Afzeliance- 

 Eucanince, RvbigiiwscB-Agrestes, Viiioscs-Toinenfosce. And 

 the remarkable thing about these pairs is that, in every 

 instance, the second members of the pairs bear the same 

 relation to the first, the EucaniiKE. differing from the Afzeliance 

 as the Rubiginosa. differ from the Agrestes and the Villosce. 

 from the Tomentosce. In each case the first section of any 

 particular pair possesses a broad, flatfish, hemispherical woolly 

 head of stigmas almost sessile on and obliterating the disk 

 (text fig. I, b), whilst the second displays less hairy and, often 

 enough, glabrous styles, more or less protruding from the disk, 

 thus leaving it clear and distinct (text fig. i, a) ; siniilarly in 

 the first section-species the sepals are more or less erect 

 and subpersistent (figs, i, 5, pi. xvi ; figs. 7, 8, pi. xvii ; fig. 

 10, pi. xviii ; fig. ;^3, pi. xx ; and pi. viii u.), whilst in the 



* Prior to any serious study of the material I had often been at a loss 

 as to how to treat the blue-green Intcliaiui and duiiicioniin forni.s ruiiiiing 

 down to the same name as their green relatives. 



