164 THE OLDER HYBRIDISTS 
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 Kélreuter 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. 
