34 ON THE ORIGIN OF SPECIES 



alluded to), would produce very vigorous seedlings, 

 which consequently would have the best chance of 

 flourishing and surviving. Some of these seedlings 

 would probably inherit the nectar - excreting power. 

 Those individual flowers which had the largest glands 

 or nectaries, and which excreted most nectar, would be 

 oftenest visited by insects, and would be oftenest crossed ; 

 and so in the long-run would gain the upper hand. 

 Those flowers, also, which had their stamens and pistils 

 placed, in relation to the size and habits of the 

 particular insects which visited them, so as to favour 

 in any degree the transportal of their pollen from 

 flower to flower, would likewise be favoured or selected. 

 We might have taken the case of insects visiting flowers 

 for the sake of collecting pollen instead of nectar ; and 

 as pollen is formed for the sole object of fertilisation, 

 its destruction appears a simple loss to the plant ; yet 

 if a little pollen were carried, at first occasionally and 

 then habitually, by the pollen-devouring insects from 

 flower to flower, and a cross thus effected, although 

 nine-tenths of the pollen were destroyed, it might still 

 be a great gain to the plant ; and those individuals 

 which produced more and more pollen, and had larger 

 and larger anthers, would be selected. 



When our plant, by this process of the continued 

 preservation or natural selection of more and more 

 attractive flowers, had been rendered highly attractive 

 to insects, they would, unintentionally on their part, 

 regularly carry pollen from flower to flower ; and that 

 they can most effectually do this, I could easily show 

 by many striking instances. I will give only one — not 

 as a very striking case, but as likewise illustrating one 

 step in the separation of the sexes of plants, presently 

 to be alluded to. Some holly-trees bear only male 

 flowers, which have four stamens producing a rather 

 small quantity of pollen, and a rudimentary pistil ; 

 other holly-trees bear only female flowers ; these have 

 a full -sized pistil, and four stamens with shrivelled 

 anthers, in which not a grain of pollen can be detected. 

 Having found a female tree exactly sixty yards from a 



