THE COMMON PRIMROSE 



These two different forms of flowers grow apart 

 on distinct plants, and although they had been 

 long recognised by botanists and gardeners, yet it 

 required the master-mind of Darwin to point out 

 the significance of their contrasting details, and to 

 reveal one of the commonest and most effectual 

 means of cross-fertilisation, not only in the Prim- 

 rose family but in numerous other groups and genera. 



It is plain that the bee, having burrowed its 

 head amongst the pollen-laden stamens in its 

 effort to reach the nectar at the base of the tube, 

 and then visiting another blossom having its stigma 

 at the mouth of the tube, must convey some of the 

 yellow pollen dust to that organ ; for the stigma 

 comes in contact with the exact part of the bee's 

 anatomy previously dusted by the stamens. Such, 

 then, are the functions of *Hhrum-eyed" and ^^pin- 

 eyed" primroses, as they are commonly called; 

 they are simply contrivances to effect cross-pollin- 

 ation by the agency of long-tongued insects. The 

 stigma is rough and sticky to receive the pollen ; 

 and when the pollen germinates and fertilisation 

 takes place, much larger quantities of seed are pro- 

 duced where the polhnation of the stigma has been 

 effected with pollen from stamens of a correspond- 

 ing level: i.e.j the ^^ thrum-e3'ed " pollen on the 

 ^' pin-eyed " stigma ; indeed, Darwin has shown 

 that only by that means can full fertility be at- 

 tained. Conversel}^ of course, the stigma of the 

 ^^ thrum-eyed " form requires pollen from the 

 stamens midway in the tube of the ''pin-eyed" 

 type. 



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