Darwin s Artificial and Natural Selection 125 



ing and surviving. The plants which produced flowers with 

 the largest glands or nectaries, excreting most nectar, would 

 oftenest be visited by insects, and would oftenest be crossed ; 

 and so in the long run would gain the upper hand and form 

 a local variety." 



The reader will notice that the sweet juice or nectar 

 secreted by certain plants is supposed to have first appeared 

 independently of the action of natural selection. Why then 

 account for its presence in flowers as the outcome of an 

 entirely different process ? If the nectar is eagerly sought 

 for by insects, without the plant benefiting in any way by 

 their visitations, why give a different explanation of its origin 

 in flowers where it is of benefit to the plant ? 



Darwin carries his illustration further: "When our plant, 

 by the above process long continued, had been rendered 

 highly attractive to insects, they would unintentionally, on 

 their part, regularly carry pollen from flower to flower ; and 

 that they do this effectually, I could easily show by many 

 striking facts. I will give only one, as likewise illustrating one 

 step in the separation of the sexes of plants. . . . As soon 

 as the plant had been rendered so highly attractive to insects 

 that pollen was regularly carried from flower to flower, another 

 process might commence. No naturalist doubts the advan- 

 tage of what has been called the ' physiological division of 

 labour ' ; hence we may believe that it would be advantageous 

 to a plant to produce stamens alone in one flower or on one 

 whole plant, and pistils alone in another flower or on another 

 plant. In plants under culture and placed under new con- 

 ditions of life, sometimes the male organs and sometimes the 

 female organs become more or less impotent ; now if we 

 suppose this to occur in ever so slight a degree under 

 nature, then, as pollen is already carried regularly from 

 flower to flower, and as a more complete separation of the 

 sexes of our plant would be advantageous on the principle 

 of the division of labour, individuals with this tendency 



