432 MU. C. DARWIN Oy THE ILLKGITIMATK OFFSPRING 



seeds, we expect as a general rule that tlieir hybrid offspring will 

 be moderately fertile ; but if the parent plants produce extremely 

 few seeds, we expect that the hybrids will be very sterile. But 

 there are marked exceptions, as shown by Gartner, to this rule. 

 So it is with illegitimate unions and illegitimate offspring ; thus 

 the mid-styled form of Lythriim Salicaria^ when illegitimately fer- 

 tilized by pollen from the longer stamens of the short- styled form, 

 produced an unusual number of seeds ; and their illegitimate off- 

 spring were not at all, or hardly at all, sterile. On the other hand, 

 the illegitimate offspring from the long-styled form, fertilized by 

 pollen from the same form, yielded few seeds, and the illegitimate 

 offspring thus produced were very sterile ; but they were more 

 sterile than might have been expected relatively to the difficulty 

 of effecting the union of the parent sexual elements, Xo point 

 is more remarkable in regard to the crossing of species than their 

 unequal reciprocity. Thus species A will fertilize B with the 

 greatest ease; but B will not fertilize A after hundreds of trials. 

 We have exactly the same case with illegitimate unions; for the 

 mid-styled Lythricm salicaria was easily fertilized by illegitimate 

 pollen from the longer stamens of the short-styled form, and yielded 

 many seeds; but the latter form did not yield a single seed when 

 fertilized by the longer stamens of the mid-styled form. 



Another important point is prepotency. Gartner has shown 

 that when two species are fertilized with each other's pollen, if 

 they be afterwards fertilized with their own pollen, or with that 

 of the same species, this is so prepotent over the foreign pollen 

 that the effect of the latter, though placed on the stigma some 

 time previously, is entirely destroyed. Exactly the same thing 

 occurs with illegitimate unions, as I ascertained in the following 

 manner: I fertilized illegitimately a long-styled common Cowslip 

 with pollen from the same form, and exactly twenty-four houi'S 

 afterwards I fertilized the same stigmas legitimately with pollen 

 from a short-styled dark-red Polyanthus. I should state that I 

 raised many seedlings from crossed Cowslips and the Polyanthus, 

 and know their peculiar appearance. I further know by the test 

 of the fertility of the mongrels, as well inter se as with both 

 parent forms, that the Polyanthus is a variety of the Cowslip, and 

 not of the Primrose {P, vulgaris) as some authors have supposed. 

 Now from the long-styled Cowslip, fertilized in the manner just 

 described, I raised thirty seedlings, everyone of which hadflowei'S 

 coloured more or less red, so that the legitimate Polyanthus-pollen 

 wholly obliterated the influence of the illegitimate Cowsbp-pollen 



