J70 GENERAL RESULTS. CHAP. XII 



of pollen from another individual or variety, although 

 the latter may have been placed on the stigma some 

 hours afterwards. The offspring from self-fertilised 

 flowers are themselves more or less sterile, sometimes 

 highly sterile, and their pollen is sometimes in an 

 imperfect condition ; but I have not met with any case 

 of complete sterility in self-fertilised seedlings, as is 

 so common with hybrids. The degree of their sterility 

 does not correspond with that of the parent-plants when 

 first self-fertilised. The offspring of self-fertilised 

 plants suffer in stature, weight, and constitutional 

 vigour more frequently and in a greater degree than 

 do the hybrid offspring of the greater number of 

 crossed species. Decreased height is transmitted to 

 the next generation, but I did not ascertain whether 

 this applies to decreased fertility. 



I have elsewhere shown * that by uniting in various 

 ways dimorphic or trimorphic heterostyled plants, 

 which belong to the same undoubted species, we get 

 another series of results exactly parallel with those 

 from crossing distinct species. Plants illegitimately 

 fertilised with pollen from a distinct plant belonging 

 to the same form, yield fewer, often much fewer seeds, 

 than they do when legitimately fertilised with pollen 

 from a plant belonging to a distinct form. They some- 

 times yield no seed, not even an empty capsule, like 

 a species fertilised with pollen from a distinct genus. 

 The degree of sterility is much affected by the condi- 

 tions to which the plants have been subjected. The 

 pollen from a distinct form is strongly prepotent over 

 that from the same form, although the former may 

 have been placed on the stigma many hours afterwards. 



* ' The Different Forms of Flowers on Plants of the same specie*, 

 1877, p. 240. 



