1867.] Relations of Verbasca. 109 



instance the homochromatic unions with yellow as female exceed in 

 fertility the converse heterochromatic union ; but in the other cases 

 given in lines 3 and 5, this higher fertility of the homochromatic unions 

 is yielded by the white variety ; the relative proportions of these being 

 much more marked than in the above cases of the heterochromatic 

 union with the yellow variety as female, viz., as 4 to 3, whereas, as w T e 

 have seen, in the heterochromatic, A. 1, the proportions are as 7 to 6. 

 In further illustrations of this point we see in B. 2 that the yellow 

 homochromatic union of V. hjchnitis, latea, by pollen of V. thcqjms, 

 lutea, relatively to the heterochromatic unions of the former with 

 pollen of V. thapsus, alba, is nearly as 5 to 4, so that we here again 

 see (as in the heterochromatic and homochroniatic unions in A 1) 

 a more intimate approximation between the products of these two 

 unions, than occurs in the other cognate unions of B. 2, in which 

 the white variety is the more fertile. 



These curious relations, however, as I have already shown, are 

 partly explained by the fact, — though we can only dimly see why it 

 should be so, — that in the pure unions of the white and yellow 

 varieties of the above mentioned species, the white, in every case, 

 yields more seed than the yellow ; whereas in the cross-unions the 

 yellow variety in general is the more productive. But, it may 

 be asked, how is the greater potency of the pollen of the white variety 

 relatively to that of the yellow variety, as shown in the above 

 tables to be accounted for ? Does it really imply that the female 

 element of the yellow variety yet retains its normal or original 

 potency, the male element alone having become absolutely less potent, 

 as compared with the male element of the white variety. This 

 hypothesis, analogically considered, does not seem to me at all 

 improbable. I think we have clearly seen by the comparative results 

 of the pure and mixed unions of the yellow variety with those of the 

 white, that the pure unions of the yellow do not yield a degree of 

 fertility at all proportionate to that of the like unions of the white 

 variety, as judged by the relative fertility of their cross-unions ; and 

 that accordingly this would seem to be due to an acquired weakness 

 in the generative powers of the yellow variety. In noticing this 

 point in a former part of, my paper, I treated it as if both sexual 

 elements had undergone a similar decrease in their generative powers ; 



22 



