MUTATION 315 



from seed in large numbers, and they have never re- 

 verted to the lamarchiana. 



"We may now take up a couple of forms, which are 

 equally constant, but which are so obviously weak as 

 to have no manifest chance of self -maintenance in 

 the wild state. These are the whitish and the oblong- 

 leaved evening-primroses or the (Enothera albida 

 and oblonga. (Enothera albida is a very weak species, 

 with whitish, narrow leaves, which are evidently in- 

 capable of producing sufficient quantities of organic 

 food. 



"O. oblonga when very young has broader leaves, 

 but in the adult rosettes the leaves become very nar- 

 row, but fleshy and of a bright green color. They are 

 so crowded as to leave no space between them unoccu- 

 pied; it always remains a small plant, reaching about 

 half the height of that of lamarchiana. 3 ' 2 



From the observation of these various species and 

 varieties of (Enothera, De Vries formulated the fol- 

 lowing laws of mutation : 



"I. The first law is, that new elementary species 

 appear suddenly without intermediate steps." 



"II. New forms spring laterally from the main 

 stem. The current conception concerning the origin 

 of species assumes that species are slowly converted 

 into others. The conversion is assumed to affect all 

 the individuals in the same direction and in the same 



2 Pp. 521-540. 



