418 Mtt. C. DAllWIN OIs' SPECIFIC DIFrKRENCES IN PRIMULA. 



towards the latter ; and we may safely eouclude that the parent 

 Oxlips had been fertilized by the surrounding Primroses. 



From the various facts now given, there can be no doubt that 

 the common Oxlip is a hybx'id betAveen the Cowslip* (P. verts ^ Brit. 

 Fl.) and the Primrose (P. vulgaris^ Brit. FL), as has been surmised 

 by several botanists. It is probable that Oxlips may be produced 

 either from the Cowslip or the Primrose as the seed-bearer, but 

 oftenest from the latter, as I judge from the nature of the stations 

 in which Oxlips are generally found t, and from the Primrose when 

 crossed by the Cowslip being more fertile than the Cowslip by the 

 Primrose, The hybrids themselves ai'e also rather more fertile 

 with the Primrose than with the Cowslip. Whether the Cowslip 

 or the Primrose be the seed-bearing plant, it is probably fertilized 

 by the opposite form of the other species ; for we have seen that 

 legitimate hybrid unions are more fertile than illegitimate hybrid 

 unions. Moreover a friend in Surrey found that twenty- nine Oxlips 

 which grew in the neighbourhood of his house consisted of thirteen 



long-styled and sixteen short-styled plants ; now,if the parent plants 

 had been illegitimately united, either the long- or short-styled form 

 would have greatly preponderated in number. The case of the 

 Oxlip is interesting ; for hardly any other instance is known of a 

 hybrid spontaneously arising in such large numbers over so wide 

 an extent of country. The common Oxlip (not the P. elatioi' of 

 Jacq.) is found almost everywhere throughout England where the 

 Cowslip and Primrose both grow, lu some districts, as I have 

 seen near Hartfield in Sussex and in parts of Surrey, specimens 

 may be found on the borders of almost every field and small wood. 

 In other districts the Oxlip is comparatively rare: near my own 

 residence I have not seen during the last twenty-five years more 

 than five or six plants or groups of plants. It is difficult to con- 

 jecture what is the cause of this diiference in number. It is almost 

 necessary that a single plant, or several plants of the same form, of 

 one parent species should grow near the opposite form of the other 

 species ; and it is further necessary that both species should be 

 frequented by the same kind of moth. It is possible that such 

 moths do not everywhere abound. 



Finally, as the Cowslip and Primrose differ in the various cha- 

 racters before specified, as they are in a high degree sterile when 



* Gcdron hns shown (Bull. Soc. Bot. de France, torn. x. (18f>3) p. 178) that 

 Primula variabilis is a hybrid between P. officinalis (i.e. P. veru<) and P. grandi- 



flora. 



t See also on this head Hiu-dwickes * Science Gossip,* 1867, pp. IH, 137. 



