CHAP. X. INCONSPICUOUS FLOWERS. 387 



group, that the progenitors of the genera Vicia and 

 Trifolium produced such minute and unattractive 

 flowers as those of V. hirsuta and T. procumbens. We 

 are thus led to infer that some plants either have not 

 had their flowers increased in size, or have actually 

 had them reduced and purposely rendered incon- 

 spicuous, so that they are now but little visited by 

 insects. In either case they must also have acquired 

 or retained a high degree of self-fertility. 



If it became from any cause advantageous to a spe- 

 cies to have its capacity for self-fertilisation increased, 

 there is little difficulty in believing that this could 

 readily be effected; for three cases of plants varying 

 in such a manner as to be more fertile with their own 

 pollen than they originally were, occurred in the 

 course of my few experiments, namely, with Mimulus, 

 Ipomoaa, and Nicotiana. Nor is there any reason to 

 doubt that many kinds of plants are capable under 

 favourable circumstances of propagating themselves 

 for very many generations by self-fertilisation. This 

 is the case with the varieties of Pisum sativum and of 

 Lathyrus odoratus which are cultivated in England, and 

 with Ophrys apifera and some other plants in a state 

 of nature. Nevertheless, most or all of these plants 

 retain structures in an efficient state which cannot be 

 of the least use except for cross-fertilisation. We have 

 also seen reason to suspect that self-fertilisation is in 

 some peculiar manner beneficial to certain plants : 

 but if this be really the case, the benefit thus derived 

 is far more than counterbalanced by a cross with a 

 fresh stock or with a slightly different variety. 



Notwithstanding the several considerations just 

 advanced, it seems to me highly improbable that 

 plants bearing small and inconspicuous flowers have 

 been or should continue to be subjected to self- 



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