HYBRIDISM 21 



ifiora with the pollen of M. jalapa, and utterly failed. 

 Several other equally striking cases could be given. 

 Thuret has observed the same fact with certain sea- 

 weeds or Fuci. Grartner, moreover, found that this 

 difference of facility in making reciprocal crosses is 

 extremely common in a lesser degree. He has ob- 

 served it even between closely related forms (as Mat- 

 thiola annua and glabra) which many botanists rank only 

 as varieties. It is also a remarkable fact that hybrids 

 raised from reciprocal crosses, though of course com- 

 pounded of the very same two species, the one species 

 having first been used as the father and then as the 

 mother, though they rarely differ in external characters, 

 yet generally differ in fertility in a small and occasion- 

 ally in a high degree. 



Several other singular rules could be given from 

 Gartner: for instance, some species have a remarkable 

 power of crossing with other species; other species of the 

 same genus have a remarkable power of impressing their 

 likeness on their hybrid offspring; but these two powers 

 do not at all necessarily go together. There are certain 

 hybrids which, instead of having, as is usual, an in- 

 termediate character between their two parents, always 

 closely resemble one of them; and such hybrids, though 

 externally so like one of their pure parent-species, are 

 with rare exceptions extremely sterile. So again, among 

 hybrids which are usually intermediate in structure be- 

 tween their parents, exceptional and abnormal individuals 

 sometimes are born which closely resemble one of their 

 pure parents; and these hybrids are almost always utterly 

 sterile, even when the other hybrids raised from seed 

 from the same capsule have a considerable degree of fer- 



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