128 Plant-Breeding 



crossing with a parent may draw the hybrid back again to 

 the parent form. So long ago as last century Kolreuter 

 proved this fact with Nicotiana and Dianthus. A hybrid 

 between Nicotiana rustica and N. panicutata was crossed 

 with N. paniculata until it was indistinguishable from it ; 

 and it was then crossed with N. rustica until it became 

 indistinguishable from that parent. Yet there is no other 

 way of fixing a hybrid to be propagated by seeds than 

 by in-breeding, and by constant attention to selection. 

 Fortunately, it occasionally happens that a hybrid is 

 stable, and therefore needs no fixing. 



Experience with egg-plants and squashes. Offspring of 

 egg-plant crosses were grown in 1890, and upon some of 

 the most promising plants some flowers were self -pollinated. 

 But these self-pollinated seeds gave just as variable offspring 

 in 1891 as those selected almost at random from the patch ; 

 and what was worse, none of them reproduced the parents, 

 or "came true to seed," and all further motive for in- 

 breeding was gone. " My labor, therefore, amounted to 

 nothing more than my own edification. My experience 

 in crossing pumpkins and squashes has now extended 

 through many years ; and, although I have obtained about 

 one thousand types not named or described, I have not 

 yet succeeded in fixing one. The difficulty here is an 

 aggravated one, however. The species are so exceedingly 

 variable that all the hybrid individuals may be unlike, so 

 that there can be no crossing between identical stocks; 

 and, if in-breeding is attempted, it may be found that the 

 flowers will not in-breed. And the refusal to in-breed is 

 all the more strange because the sexes are separated in 

 different flowers on the plant. In other words, in my 



