In Table 3 we have first the results of the pure unions of V. lychnitis, 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: 82. By the hybrid-unions of V. lychnitis, alba, with the pollen of V. phoeniceum, alba, a slightly higher degree of sterilisation results; the proportion in this case being as 82: 67, 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, lutea. Thus the pollen of V. phoeniceum, 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. phoeniceum, 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 flowers are the more fertile. V. lychnitis, lutea, yielding with pollen of V. thapsus, lutea, 46, and with the pollen of V. thapsus, alba, 39, relatively to 100,.

the 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. blattaria and V. thapsus with the V. lychnitis. In the unions, however, of V. phoeniceum 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.

The results of experiments on the V. blattaria, varieties lutea and alba. are given in the above Tables: they comprise 12 unions between the white and yellow varieties of three species. Let us briefly compare the results of their reciprocal unions. First, the fertility of V. blattaria, alba, when fertilised by its own pollen. undergoes the highly proportionate sterilisation of 98: 78 when fertilised with the pollen of the yellow variety-V. blattaria, lutea. In the converse case, the sterilising influence of the cross relatively to the pure unions of these forms is much decreased, the pure union of V. blattaria, lutea, yielding more seed in the proportions of 90: 88 than from its cross-union with the white variety-V. blattaria, alba. Secondly, as to the hybrid unions with the pollens of the yellow and white varieties of V. thapsus. In these the pollen of the white variety is the more potent. Thus V. blattaria, alba, fertilised by pollen of V. thapsus, alba, affords an average fertility of 43, whereas by that of V. thapsus, lutea, the produce is reduced to 32, relatively in both cases to 100, the average fertility of V. blattaria, alba, when fertilised by its own pollen. By the union of the yellow and white varieties of V. thapsus with the yellow variety of V. blattaria, we see that the relative differences in the

potency of the two pollens on the stigmas of V. blattaria, lutea, are much less than those we have above noticed when V. blattaria alba is used as female; and also that the potency of the two pollens is greater on the stigmas of the yellow than those of the white variety of V. blattaria lutea; and again that the white variety of V. thapsus is more fertile than the yellow, in their respective unions with the V. blattaria, alba. Thus V. blattaria, lutea, by pollen of V. thapsus, alba, gives an average fertility of 61; by pollen of V. thapsus, lutea, 50, relatively to 90, the product of fertilisation by its own pollen. Lastly, we have the different unions of the two pollens of the white and yellow V. lychnitis on the stigmas of the yellow and white varieties of I. blattaria. In these unions we see first that with V. blattaria, alba as female, the pollen of the white variety exceeds that of the yellow in the proportion of 36:23; secondly, with the V. blattaria, lutea, as female, the pollen of the white variety is again singularly enough the more fertile, exceeding that of the yellow variety, in the proportion of 45: 41. Thirdly, we find that here also the yellow variety of V. blattaria yields a higher degree of fertility,—taking the conjoint products of the two unions with the pollen respectively of V. thapsus, lutea and alba,—than the white variety of V. blattaria when similarly treated, the proportions being as 70 of the V. blattaria to 47 of the V. blattaria, alba, or nearly as 3 : 2.

This leads me to notice a curious fact prominently brought before us in the above Table, whatever may be its real signification, namely, that the yellow varieties of V. lychnitis and blattaria, though yielding a higher grade of fertility to the pollen of the white and yellow varieties of distinct species than do the respective white varieties of the above species when similarly fertilised, are nevertheless less productive of seed than the white, when both are fertilised with their own pollen. This will be seen by consulting the following tabular arrangement, in which I have given a reduced approximate of the relative fertility of the different unions, selecting from the hybrid unions in each instance only the most fertile.

1. V. lychnitis, alba, by own pollen is as 83: 75 of V. lychnitis, lutea, by its own pollen.

2. V. lychnitis, alba, by pollen of V. lychnitis, lutea, is as 68:71 of V. lychnitis, lutea, by pollen of V. lychnitis, alba.