172 On the Re-productive Functional [No. 3, 



from my previous remarks on the co-relations between the degree of 

 fertility and affinity of colour in the crossing of varieties of a species, 

 together with the results of the hybridising differently coloured varie- 

 ties of distinct species, this law seems clearly indicated, that the 

 relative degree of fertility of the cross unions between the differently 

 coloured varieties of certain species is inversely proportionate to the 

 less or more mediate colour affinities of these unions. Further that 

 this law does not extend to, or regulate the hybrid unions of differ- 

 ently coloured varieties of distinct species, but is strictly limited in 

 its operations to those anions of varieties of a single species. Such 

 at least is the conclusion which my own experiments would induce 

 me to hold, but seeing that they are so directly opposed to the results 

 of Gartner's large experience, I would rather avoid at present any- 

 thing like definite or positive conclusions, until subsequent experi- 

 ment affords us a crucial array of data. 



In conclusion, I will now by a cursory retrospect of the above de- 

 tails, re-state a few of the more important points, which elucidate the 

 mooted relations between the phenomena of the hybridisation of a species 

 and the mongrelism of the varieties of a species. First then in hybridism 

 we see on the calculation of Y. lychnitis yielding with its 

 own pollen 100 seeds, it yields upon fertilisation with pollen of 

 V. nigrum 80 seeds, by the pollen of V. virgatum 58 seeds, by 

 that of V. phceniceum 66 seeds and by that of Y. thapsiforme 46 

 seeds. In the unions of varieties of a species, with these of other 

 species we find differences in the sexual powers, so that the pollen of 

 the one variety of a species is less potent than that of the other 

 on the stigmas of the same variety of another species. Thus V. 

 lychnitis fertilised by the pollen of V. Uattaria, lutea, yields 

 51 seeds, by that of Y. Uattaria, alba, 56 seeds, and again by 

 pollen of Y. thapsus, lutea, Y. lychnitis yields 46 seeds, by that 

 of Y. thapsus, alba, 39 seeds, relatively in each case to the 100 

 seeds produced by its own pollen. Again we have evidence also of 

 reciprocal differentiation in the relative sexual powers of varieties of a 

 species, and those of other species. Thus in the case mentioned above 

 of V. Uattaria, the pollen of variety alba is more potent on the 

 stigma of Y. lychnitis than that of variety lutea, whereas in the 

 converse unions of these forms, we find that the pollen of Y. 



