THK UKNUS ROSA 285 



growing to a height of ten to twelve feet, twice the 

 usual height of the sweet briar {Rosa rubiginosa), which 

 again is usually a taller plant than the Scotch rose {R. pitn- 

 pinellifolia). Like the other hybrids which I have mentioned 

 it forms clumps rather than bushes. In this point we see 

 clearly the influence of R. pitnpinellifolia. This sends out 

 numerous suckers from the roots, which themselves produce 

 roots, and soon produce a thick cluster of daugliter plants 

 around the parent stock. All its hybrids partake of the same 

 character, and I have seen a clump of R. involuta extending 

 for a distance of 20 yards, the whole evidently having arisen 

 from one single original plant." 



Modern Conceptions regarding them. 



Since Christ made his original determinations the study 

 of roses has been revolutionised, and, in spite of the silly 

 erection of multitudes of " sawdust " species, microgenes 

 which actually exist, and therefore can be recognised in the 

 field, have been described. Further, their systematic positions 

 have been accurately made out. As a result we have the 

 separation of the Afzeliance from the original EucanincB^ the 

 Agrestes from the Rnbiginosce, and the Tonientos(Z from the 

 Villosce. No longer does it suffice to say that Rosa hibernica^=- 

 R. pimpinellifoliaX R. canina. R. canina, when that diagnosis 

 was first made by Fries, was a very comprehensive aggregate. 

 To British authors not obsessed with the splitting mania, it now 

 breaks into four* collective species, R coriifolia, R. glauca, 

 R. canina and R. dumetorum. Each of these possesses 

 numerous microgenes, eacli of which may be involved in a 

 cross with R. pitnpinellifolia. Still, let us note, the oppor- 

 tunities for crossing are not very great ; differences in habitat 

 and time of flowering interpose very effective barriers, so that 

 even to this day hybrids of this type remain very rare. They 

 do, however, occur both in the north and in the south of our 

 island. If they appear in the south, since R. glauca (agg.) 



*I only admit two, for I regard the first pair and the second pair as each 

 forming an aggregate species. 



