ON THE ORIGIN OF NEW SPECIES 



time and dying; or separating where united; or 

 bearing one or two crops of fruit and then 

 suddenly blighting; or separating after years of 

 growth up to complete congeniality. So it is 

 in crossing, — all grades of hybridity are to be 

 found. Crossed plants generally have the 

 characteristics of both parents combined, yet 

 sometimes show their parental influences on 

 one side, producing uncertain results in the 

 first generation. In the second and succeeding 

 generations these cross-bred seedlings usually 

 break away into endless forms and combi- 

 nations, sometimes reverting to some strange 

 ancestral form which existed in the dim past. 

 Or the break may not occur until after many 

 generations. But when once the old, persist- 

 ent type is broken up, the road is open for 

 advances in any useful direction. Sometimes 

 hybridized or crossed seedlings show consider- 

 able, or even great, variation for weeks; or 

 they may show no change in foliage or growth 

 from one or the other parent form until 

 nearly ready to bloom or bear fruit, when 

 they suddenly change in foliage, growth, char- 

 acter and general appearance." 



This question of the origin of new species 



819 



