THE GENUS ROSA 263 



From this table the astounding position emerges that, of 36 

 of our wild and subspontaneous roses and two garden hybrids 

 produced from them, only four possess perfect pollen, three 

 approach these, whilst no less than 75 per cent, have more 

 than half of their microspores imperfect, and still more 

 significantly, some 40 per cent, of the whole can only display 

 at best less than 10 per cent, of well-formed pollen capable of 

 bringing about fertilisation. Lastly, seven forms, two certainly 

 hybrids, produced practically no good pollen. And matters 

 are much worse than the table suggests, for whilst only a 

 comparatively small number of the microgenes showing 

 aborted pollen were examined quantitatively, and therefore 

 tabulated, all of those with above 50 per cent, good grains are 

 included. 



Whence, if pollen conditions may be invoked as a criterion 

 of hybridity, it appears certain that almost all of our wild 

 roses are latent hybrids, Rosa pimpinellifolia, R. 7nollis, 

 R. omissa and R. senticosa being more or less honourable 

 exceptions amongst the genuine natives, and R. cinnamomea 

 and R. rugosa amongst the introduced and half-wild forms. 



At the lower end of the scale the most noteworthy feature 

 lies in the preponderance of the Afzeliance in the worst class, 

 in the massing of the Rubiginosce in their neighbourhood, and 

 the presence of the Villosa form caendea in the same category. 

 In all of these cases the matter is complicated by the 

 occurrence of facultative apomixis. Despite this, as with all 

 other microgenes, it appears almost certain that the pollen 

 sterility is the outcome of latent hybridity, and the apomixis, 

 therefore, a secondary effect of the same. Any discussion on 

 this point will be reserved until the latter phenomenon comes 

 up for treatment. 



But if so many of our roses are thus contaminated, and 

 Rosa pimpinellifolia, R. mollis, R. omt'ssa, R. senticosa, of the real 

 natives, and R. rugosa and R. cinnamomea of the others, have 

 to a very great extent escaped, there must be some reason for 

 their favoured position. Let us carefully consider each of these 



