ON PRIMROSES AND THEIR FERTILIZATION. 89 



without the pistil being fertilized by pollen scattered 

 ou it from the anthers. Now what follows from 

 this ? We have first a short-styled variety, the 

 anthers reaching some height above the stigma ; it is 

 easy enough to imagine how the pollen may drop from 

 these anthers on the stigma and so fertilize it. But 

 what about the long- styled pin centre, where the 

 stigma stands above the pollen bearing organs, and 

 so does not stand any chance of being thus fertilized ? 

 Now the first thought that struck Mr. Darwin was 

 this, that the primrose was gradually becoming 

 dioecious, i.e. that by and by the stamens would die 

 out in the long-styled specimens, and the plant 

 would bear only a pistil ; and that in the short- sty led 

 specimens the pistil was dying out and the stamens 

 were developing themselves. It is the case in many 

 plants that some flowers bear pistils only and others 

 stamens only they are called dioecious or " Re- 

 housed. " Thus in time we should get two sorts of 

 primroses much more distinct than they are at 

 present. Again, the thought may strike you at once, 

 that if the pollen cannot reach the stigma on the 

 long- sty led specimens there can be no fertilization, 

 and therefore no seed, and consequently the pin cen- 

 tres must in time die out. Now we must ask some 

 botanical friend whether he knows for a certainty 

 that the pin centres ever produce seed. He savs 



j. j. t/ 



" Yes, quite as often as the others." Therefore they 

 do get fertilized. This sets us thinking again how ? 

 Mr. Darwin says it is done by the Humble Bee. 

 Many of you will recollect how by the agency of this 

 and other insects orchids are fertilized. The bee 

 inserting its head into the corolla of a flower detaches 



