Chap. II. THE COMMON OXLIP. 63 



natural treatment ; but not one of them presented the 

 least variation except in size — those in the peat at- 

 taining almost gigantic dimensions, and those in the 

 clay being much dwarfed. 



I do not, of course, doubt that cowslips exposed 

 during several successive generations to changed con- 

 ditions would vary, and that this might occasionally 

 occur in a state of nature. Moreover, from the law 

 of analogical variation, the varieties of any one species 

 of Primula would probably in some cases resemble 

 other species of the genus. For instance I raised a red 

 primrose from seed from a protected plant, and the 

 flowers, though still resembling those of the primrose, 

 were borne during one season in umbels on a long foot- 

 stalk like that of a cowslip. 



With regard to the second class of facts in support 

 of the cowslip and primrose being ranked as mere 

 varieties, namely, the well-ascertained existence in a 

 state of nature of numerous linking forms* : — If it can 

 be shown that the common wild oxlip, which is inter- 

 mediate in character between the cowslip and prim- 

 rose, resembles in sterility and other essential respects 

 a hybrid plant, and if it can further be shown that the 

 oxlip, though in a high degree sterile, can be fertilised 

 by either parent-species, thus giving rise to still finer 

 gradational links, then the presence of such linking 

 forms in a state of nature ceases to be an argument 

 of any weight in favour of the cowslip and primrose 

 being varieties, and becomes, in fact, an argument on 

 the other side. The hybrid origin of a plant in a 

 state of nature can be recognised by four tests : first, 

 by its occurrence only where both presumed parent- 



* See ati excellent article on in the ' Pliytologist,' vol. iii. p 

 this subject by Mr. H. 0. Watson 43. 



4 



