KOLREUTER 153 



stigmas of the hybrid plants, a certain number of seeds 

 capable of germination was obtained, although this 

 number was much smaller than in the case of normal 

 fertilization of either parent species. This partial 

 sterility, affecting in particular the stamens and the 

 pollen which they produce, is a feature common to the 

 majority of hybrids between different natural species. 

 Many such hybrids, indeed, are altogether sterile, so 

 that a further generation cannot in any way be ob- 

 tained from them. On the other hand, the members 

 of different strains or varieties which have arisen under 

 cultivation yield, as a rule, when crossed together off- 

 spring which are perfectly fertile. 



In subsequent years Kolreuter was able to obtain a 

 very few self-fertilized offspring from hybrids of the 

 same origin as the above. The resulting plants were 

 described as resembling their hybrid parent so closely 

 as to be practically indistinguishable from it. 



The offspring obtained by crossing the hybrid plants 

 with pollen from either parent showed in each case a 

 form more or less intermediate between that of the 

 original hybrid and that of the parent species from 

 which the pollen was derived. But the plants were 

 not all alike in this respect, some of them being much 

 more like the parent species than others, and some, 

 again, varying in other directions. There were also 

 considerable differences between the different indi- 

 viduals in respect of fertility, so that some of the 

 plants were more and some less sterile than the original 

 hybrids. Also, there was some tendency to the produc- 

 tion of malformations of the flowers and other parts. 



