KOLREUTER 163 



stigma, or by the agency of the wind, or, lastly, the 

 pollen may be carried by insects visiting the flowers. 

 And he recognised many features characteristic of 

 flowers apt to be fertilized in one or other of these 

 ways in particular. Thus he was aware, for example, 

 of the nature and use of the nectar which so many 

 flowers produce namely, that it is the substance from 

 which the bees by far the most diligent visitors of 

 flowers obtain their honey. 



Curiously enough, Kolreuter was not aware of the 

 existence of any natural wild hybrid plants. But he 

 was quite right in contending that supposed examples 

 of such hybrids required for their substantiation the 

 experimental proof, which could only be afforded by 

 making actual artificial crosses between the putative 

 parent species. 



The first hybrid made artificially by Kolreuter was 

 obtained in 1760 by applying the pollen of Nicotiana 

 paniculata to the stigma of Nicotiana rustica. The 

 hybrid offspring of this cross showed a character inter- 

 mediate between those of the two parent species in 

 almost every measurable or recognisable feature, with 

 a single notable exception. This exception was 

 afforded by the condition of the stamens and of the 

 pollen grains produced by the hybrids. These organs 

 were so badly developed that in all the earlier experi- 

 ments self-fertilization of the hybrid plants yielded no 

 good seed at all, nor were the pollen grains of the 

 hybrid any more effective when applied to the stigmas 

 of either of the parent species. On the other hand, 

 when pollen from either parent was supplied to the 



II 2 



