THE ORIGIN OF SPECIES AND GENERA 275 



plants with large yellow flowers of American 

 importation. In a fallow field near Hilversum, 

 invaded by (Enothera Lamarckiana, he noticed 

 among this species many monstrous varieties, 

 some with twisted stems, others with branches 

 stuck together, others, again, with concave leaves 

 or petals in varying numbers. Among these 

 abnormal forms, two especially were remarkable 

 from the absence of individuals intermediate either 

 between each other or between these varieties and 

 the parent type. They were two true species, till 

 then unknown, and, without any possible doubt, 

 were detached from (Enothera Lamarckiana within 

 less than twenty-five years. These new species 

 have retained their characteristics with constancy 

 in all the cultures made by this scholar on thou- 

 sands of plants. The origin of these new QEnotheras 

 can only be explained by the fact of an abrupt 

 apparition of abnormal individual plants having, 

 perhaps, undergone during their seed life, as occurs 

 in the Cardere, an accidental modification which 

 is betrayed by an equally abrupt variation in the 

 adult plant. These variations are indefinitely 

 kept up by heredity, so that there is no excuse for 

 refusing them the title of species. 



Nilsson has obtained similar results by observing, 

 in the laboratory of Svalof , in Sweden, the abrupt 

 variations arising in the ears of divers kinds of 

 cereals. A few of these variations advantageous 

 to agriculture constitute veritable new species, 

 the characteristics of which are kept constant by 

 heredity under all conditions of environment. 



As to the ultimate cause of these abrupt varia- 



