368 Origin of Each Species Considered Separately. 



constant one; moreover It seems to make no difference 

 whether the Lamarckianas are of pure strain or the off- 

 spring of crosses. 



This conclusion is supported by the proportions in 

 which O. nanella occurs in crops raised directly from 

 crosses, that is, in the first generation after the cross. 

 The foregoing table referred to the second generation 

 from artificial crosses, or from free crossing as in the 

 case of O. laczi folia. 



INDIVIDUALS OF O. NANELLA WHICH HAVE ARISEN BY 



MUTATION. 



Totals 5696 46 0.8 



If we compare these figures with those already given 

 for other species we find a striking agreement between 

 them and those for 0. ohlonga (about 1 %) and we may 

 therefore regard 0. nanella as one of the commoner 

 forms. It may also be regarded as parallel in this respect 

 with 0. lata which will be described afterward (§ 22) and 

 possibly with O. albida which however appears in varying 

 proportions. 0. riihrinervis, O. gigas, and O. scintillans 

 on the other hand form a quite distinct group of rarer 

 mutations, whilst O. semilata and the other less important 

 types form a third group of still rarer deviations. 



