308 ^ SIZE OP THE COEOLLA. Chap. VII. 



amara, Oeranium sylvaticum, Myosotis, and Salvia. 

 On the other hand, as Von Mohl remarks, when a 

 plant produces hermaphrodite flowers and others 

 which are males owing to the more or less complete 

 abortion of the female organs, the corollas of the 

 males are not at all increased in size, or only excep- 

 tionally and in a slight degree, as in Acer.* It seems 

 therefore probable that the decreased size of the female 

 corollas in the foregoing cases is due to a tendency to 

 abortion spreading from the stamens to the petals. We 

 see how intimately these organs are related in double 

 flowers, in which the stamens are readily converted 

 into petals. Indeed some botanists believe that petals 

 do not consist of leaves directly metamorphosed, but of 

 metamorphosed stamens. That the lessened size of the 

 corolla in the above case is in some manner an indirect 

 result of the modification of the reproductive organs is 

 supported by the fact that in Bhamnus eatharticus not 

 only the petals but the green and inconspicuous sepals 

 of the female have been reduced in size ; and in the 

 strawberry the flowers are largest in the males, mid- 

 sized in the hermaphrodites, and smallest in the fe- 

 males. These latter cases, — the variability in the size 

 of the corolla in some of the above species, for instance 

 in the common thyme, — together with the fact that it 

 never differs greatly in size in the two forms — make 

 me doubt much whether natural selection has come 

 into play; — that is whether, in accordance with H. 

 Miiller's belief, the advantage derived from the pol- 

 leniferous flowers being visited first by insects has 

 been sufficient to lead to a gradual reduction of the 

 corolla of the female. We should bear in mind that as 

 the hermaphrodite is the normal form, its corolla has 



* ' Bot. Zeitung,' 1863, p. 326. 



