68 HYBRID PRIMULAS. CHAP. II 



illegitimately fertilising, 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 17) 

 was nearly as fertile as if both parents had been pure. 

 A short-styled primrose legitimately fertilised by the 

 long-styled oxlip (Table 18) also yielded a moderately 

 good average, namely 48 7 seeds ; but if this short- 

 styled primrose had been fertilised by a long-styled 

 primrose it would have yielded an average of 65 seeds. 

 If we take the ten legitimate unions together, and the 

 ten illegitimate unions together, we shall find that 29 

 per cent, of the flowers fertilised in a legitimate manner 

 yielded capsules, these containing on an average 27 4 

 good and bad seeds ; whilst only 15 per cent, of the 

 flowers fertilised in an illegitimate manner yielded 

 capsules, these containing on an average only 11 '0 

 good and bad seeds. 



In a previous part of this chapter it was shown that 

 illegitimate crosses between the long-styled form of 

 the primrose and the long-styled cowslip, and between 

 the short-styled primrose and short-styled cowslip, are 

 more sterile than legitimate crosses between these two 

 species ; and we now see that the same rule holds good 

 almost invariably with their hybrid offspring, whether 

 these are crossed inter se, or with either parent-species ; 

 so that in this particular case, but not as we shall pre- 

 sently see in other cases, the same rule prevails with 

 the pure unions between the two forms of the same 

 heterostyled species, with crosses between two distinct 

 heterostyled species, and with their hybrid offspring. 



Seeds from the long-styled oxlip fertilised by its 

 own pollen were sown, and three long-styled plants 

 raised. The first of these was identical in every 

 character with its parent. The second bore rather 



