446 MB. C. DABWIN ON SPECIFIC DirrERENCES IN PEIMrLA. 



We will first consider the results, as shown in the two left-hand 

 compartments in the five Tables, obtained from the short-styled 

 Ozlip when crossed with the long-styled Oxlip, and when crossed 

 with both forms of the Cowslip and Primrose. I may premise that 

 the pollen of two of the short-styled Oxlips consisted of nothing 

 but minute aborted whitish cells ; but in the third plant about 

 one-fifth of the grains appeared in a sound condition. Hence it 

 is not surprising that neither the short-styled nor the long-styled 

 Oxlip produced a single seed when fertilized by this pollen. Nor 

 did pure Cowslips or Primroses when illegitimately fertilized by it; 

 but when legitimately fertilized they yielded a few good seeds. The 

 female organs of the short-styled Oxlips, though greatly deterio- 

 rated in power, are in a rather better condition than the male 

 organs j for though the short-styled plants yielded no seed when 

 fertilized by the long-styled Oxlip, and hardly any when illegiti- 

 mately fertilized by pure Cowslips or Primroses, yet when legiti- 

 mately fertilized by these latter species, especially by the long- 

 styled Primrose, they yielded a moderate supply of seed. 



The long-styled Oxlip was more fertile than the short-styled, 

 and about half the polleu-grains appeared sound. It bore no seed 

 when legitimately fertilized by the short-styled Oxlip ; but this no 

 doubt was caused by the badness of the pollen of the latter ; for 

 when illegitimately fertilized (Table I.) by its own pollen it pro- 

 duced some good seeds, though much fewer in number than self-fer- 

 tilized pure Cowslips or Primroses would have produced. The long- 

 styled Oxlip likewise yielded a very low average of seed, as may be 

 seen in the third compartments in the TableSj when illegitimately 

 fertilized by, and when illegitimately fertilizing, pure Cowslips and 

 Primroses. The four corresponding legitimate unions, however, 

 were moderately fertile, and one (viz. that between a short-styled 

 Cowslip and the long-styled Oxlip in Table lY.) was nearly as 

 fertile as if both parents had been pure. A short-styled Primrose 

 legitimately fertilized by the long-styled Oxlip (Table V.) also 

 yielded a moderately good average, namely 48'7 seeds ; but if the 

 short-styled Primrose had been fertilized by a pure long-styled 

 Primrose it would have yielded an average of seventy-seven seeds. 

 In a previous part of this paper it was shown that a cross between 

 the same forms of the Primrose and Cowslip is more sterile thau 

 a cross between the two opposite forms ; and we now see in these 

 latter Tables that the same rule almost invariably holds good with 

 crosses between hybrids and tlie two pure parent species ; so that 



