The Periodicity of Progressive Mutations. 655 
Knwffi 
Fig. 149. Schematic pedigree of progressive formation of 
species; based on Ocnothera Lamarckiana. The upper 
group is a reduced form of Fig. 148, and contains the 
same new species. Onagra is the sub-genus to which 
Ocnothera Lamarckiana belongs. Euocnothera, Knciffia 
and Xylopleurum are other sub-genera of Ocnothera. 
The two small groups of lateral branches which have 
been intercalated are intended to represent the several 
intermediate periods of mutation. The figure can be 
continued downwards in a similar manner. 
