258 DR. J. W. HESLOP HARRISON ON 



the Lithium-Sodium-Potassium subgroup and the Copper- 

 Silver-Gold subgroup. Again, the Semivillosan R. faroejisis 

 and R. orientalis, with R. pimpinellifolia, suggest in a striking 

 way the transitional elements in the chemist's group eight. 

 Lastly, it would not be a surprising thing should it turn out 

 in the end that the parallel nature of the two tables is founded 

 on chemical differences of the same type. 



Thus Almquist working as a systematist, and I as a 

 geneticist, arrived at essentially the same conclusions and 

 announced them at practically the same period. 



To fit the Cinnamomece into the general arrangement was 

 not difficult, for the only two forms of that section known to 

 me form by far the most beautiful and clearest illustration of 

 the differences between the clear green and glaucous micro- 

 genes I have examined. Rosa punpitiellifolia (figs. 18, 19, pi. xix) 

 on the other hand, completely defeated my efforts. After cyto- 

 logical examination, which determined that the CanincE. were 

 endowed with a chromosome complement of 28 (haploid 

 numbers) and the Pimpinellifolice with 14, I regarded these 

 discrepancies as the cause of the unconformability. However, 

 the acumen of Almquist in devising his table had not been 

 lacking here. He points out that the leaflets on its flowering 

 shoots have in. no case advanced beyond the stage of the 

 lower leaves of R. Traaeui. Any comparison of its leaf 

 characters with those of other roses can only be with those of 

 such lower leaves. If we recognise this, then it agrees with 

 the non-committal and primitive TraaeJii leaflet referred 

 to previously as a possible point of derivation of all leaf 

 forms. 



Further, he adds the interesting remark that its stem with 

 its closely set prickles stops short at the secoiid year's stage of 

 other roses. In both of these points, leaflets and armature, 

 R. pimpinellifoiia reveals itself as a juvenile species such as is 

 seen elsewhere in the genus Clematis. Another very ini[)ort- 

 ant fact also emerges ; although R. pimpinellifoiia is the only 

 rose known from Iceland, and although the Icelandic form is 



