56 HYBEID PEIMULAS. Chap. U. 



where, Ofving to the frequency of this intermediate 

 hybrid form, and to the existence of the Bardfield 

 oxlip (P. elaiior), which resembles to a certain extent 

 the common oxlip, the claim of the three forms to 

 rank as distinct species has been discussed oftener 

 and at greater length than that of almost any other 

 plant. Linnaeus considered P. veris, vulgaris and 

 elatior to be varieties of the same species, as do some 

 distinguished botanists at the present day ; whilst 

 others who have carefully studied these plants do not 

 doubt that they are distinct species. The following 

 observations prove, I think, that the latter view is 

 correct ; and they further show that the common oxlip 

 is a hybrid between P. veris and vulgaris. 



The cowslip differs so conspicuously in general ap- 

 pearance from the primrose, that nothing need here 

 be said with respect to their external characters.* 

 But some less obvious differences deserve notice. As 

 both species are heterostyled, their complete fertili- 

 sation depends on insects. The cowslip is habitually 

 visited during the day by the larger humble-bees 

 (viz. Bombus musoorum and hortorum), and at night 

 by moths, as I have seen in the case of Gucullia. The 

 primrose is never visited (and I speak after many 

 years' observation) by the larger humble-bees, and 

 only rarely by the smaller kinds; hence its ferti- 

 lisation must depend almost exclusively on moths. 

 There is nothing in the structure of the flowers of the 

 two plants which can determine the visits of such 

 widely different insects. But they emit a different 

 odour, and perhaps their nectar may have a different 

 taste. Both the long-styled and short-styled forms of 



* The Eev. W. A. Lelghton seed, in > Ann. and Mag. of Nat. 

 has pointed out certain differences Hist.' 2nd series, vol. ii. 1818, 

 in the form of the capsules and p. 164. 



