510 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 1908. 



caution was taken to exclude interference of agencies which might 

 introduce errors. It is impossible to describe the enormous amount 

 of work entailed in such investigations, but the truly splendid results 



Fig. 1. — Oenothera Lainarckiana, the parental form which is giving off many mutants. 

 A, B, and C, leaves from rosette ; D, leaf from middle of flowering stem ; E, bract ; 

 F, flower with petals removed ; G, petal. 



well justify the tedious care by which lines of descent were carried 

 through successive generations for two decades without allowing a 

 trace of doubt as to the purity of the lineage involved. 



