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In addition to the simple and calculated results given on Table 1, I have, in the above, given at the right hand, for the sake of comparison, the calculated product from an assumed 1,000 seeds of the pure unions relatively to those yielded by the cross and hybrid unions. By a further comparative study of these results, we find that the fertility of the pure unions of V. phaniceum, relatively to that of its cross-unions with the white and rose-coloured varieties, is, in the least differentiated or most highly fertile unions, viz., V. phaniceum, rosea by pollen of V. phceniceum, as 100: 95; whereas in the least fertile unions, V. phaniceum by pollen of V. phcrniceum, alba, the proportions are as 100 : 56. The averago fertility of the Jive cross-unions given in the table, relatively to the pure unions given in the first lino, is as 100 : 75; so that the pure unions thus exceed in foitility the cross-unions, in nearly the proportions of 4:3. Again by a similar comparative study of the relative fertility of the pure unions of V. phceniceum and the different hybrid unions given in the Table, we find that the highest degree of fertility results from the union of V.ferrugineum (which perhaps is correctly regarded by De Candolle and others as a mere variety of V. phceniceum) with V. phceniceum, the proportions of the pure to the hybrid unions being as 100 : 59, in favour of the former. The lowest degree of fertility results from the anions of V. ovali/olium, with V. phceniceum, the proportion of the pure to the hybrid-unions in this case being as 100 : 24.) Lastly the average fertility of the five hybrid unions given in the latter lines of the Table, relatively to the pure unions of V. phceniceum, is nearly as 100 : 40, or as 2.5 seeds of the pure unions to one of the hybrid onions. Thus, the relative differences in the degree of sterilisation resulting from the hybridisation of distinct species, and that from the cross-impregnation of varieties of a species, relatively in either case to the pure unions, is in the former as 2.5 : 1, and in the latter as 4 : 3.
In Table 3 we have first the results of the pure unions of V. hjchnitis, alba, and by comparing them with those resulting from fertilisation with the pollen of V. lychnitis, lutea, we find that the latter cross-unions undergo the proportionately decreased fertility of 100 : $'2. By the hybrid-unions of V. lychnitis, alba, with the pollen of V. phecniceum, alba, a slightly higher degree of sterilisation results; the proportion in this case being as 82 : 07, relatively to 100 produced by the pure unions of V. lychnitis, alba. The highest degree of sterilisation in this Table results from the union of V. lychnitis, alba, by pollen of V. thapsus, alba, the proportion of the pure to the hybrid unions being here as 100 : 47.
The results of my experiments on the yellow variety of V. lychnitis are given in Table 4. By a comparative examination of this Table,we have the following general results: first, the fertility of the pure unions of V. lychnitis, lutea exceeds that resulting from the cross-unions of the latter with pollen of V. lychnitis, alba, in the proportion of 100 : 94. The degree of sterilisation induced by these unions, though less than that resulting from the converse unions given in Table 3, is nevertheless sufficient to show a sterilising influence in the conjunctions of varieties of a species, characterised only by those, systematically considered, trifling differences in colour—the one being white, the other yellow. Secondly we have the results of unions of similarly and dissimilarly coloured forms of distinct species, with V. lychnitis, httea. Tuns the pollen of V. phceniceum, with purplish coloured flowers, applied to the stigmas of V. lychnitis, lutea, gives an average fertility of 66; the pollen of the white variety V. phceniceum, alba, gives an average of 55; while that of the rose-coloured variety is productive of the highest degree of sterilisation, giving only 49—relatively to 100, the produce of V. lychnitis, lutea by its own pollen. Mr. Darwin, on the authority of Gartner, states in his " Origin of Species," that similarly coloured varieties of distinct species are more fertile when crossed than are the dissimilarly coloured varieties of the same species. The particular illustration of this point will be found in a subsequent part of this paper ; I will here merely state that, in the above unions, the degrees of fertility are by no means regulated by the colour affinities. Thus, we have first yellow and violet, then yellow and white, and lastly yellow and rose yielding a successively decreased fertility ; whereas, judging by the colour affinities, the arrangement ought to have been, beginning with the most fertile, yellow first with white, then with rose, and lastly with violet. Secondly, with pollen of the V. blattaria, vars. alba and lutea, we see, that the V. lychnitis, lutea yields the higher degree of fertility with the former: V. lychnitis, lutea, yielding with pollen of V. blattaria, alba, 56, and with that of V. blattaria, lutea, 51, relatively to 100, the product of fertilisation with its own pollen. Thirdly, in the unions of V. lychnitis, lutea, by pollen of the yellow and white varieties of V. thapsus, we find that unions of the similarly coloured llowers are the more fertile. V. lychnitis, lutea, yielding with pollen of V. tliapsus, lutea, 46, and with the pollen of V. thapsus, alba, 39, relatively to 100, . thc results of fertilisation with its own pollen. Fourthly, in accordance with recognised systematic affinities, we find the following descending scale of sterilisation resulting from the unions of V. nigrum, V. virgatum and V. thapsiforme with the V. lychnitis. Thus with the pollen of V. nigrum, the average fertility of V. lychnitis, lutea, is 80, with that of V. virgatum 58, and with that of V. thapsiforme 46, relatively, in each instance, to 100, the product of fertilisation by its own pollen. A similar accordance is observable between the functional and systematical relations of V. hlattaria and V. thapsm with the V. lychnitis. In the unions, however, of V. phceniceum and varieties with the V. lychnitis, no such accordance is observable. The different unions vary greatly in the degree of fertility inter se, and judging indeed by the relative functional potency of the pollen of the three varieties on the stigmas of V. lychnitis, the different results are comparable with those from distinct species, and would cause their interpolation into systematically considered false positions, showing us that the functional and systematic affinities of the species of a genus are by no means strictly co-ordinated.