Oenothera Lamarckiana Seringe. 439 



Later systematists have either lumped all these forms 

 into one big species or have separated them up in differ- 

 ent ways. When they did the former, they took O. 

 biennis as a type. The other species were ranged round 

 this as varieties. This was done for example by Torrey 

 and Gray in their famous Flora of North America and 

 by Watson in his monograph. This is an important 

 point for our further discussions, as showing that a 

 minute comparative study of the various forms points 

 to their common origin from O. biennis. 



Spach however thinks differently. He separates six 

 species of Onagra. Two of them include all the forms 

 which interest us; the rest are rare and do not exist in 

 Europe either as wild or as cultivated forms. These two 

 species are (1) Onagra vulgaris Spach = Oenothera 

 biennis L; but also including O. suaveolens Desf. and O. 

 Lamarckiana Ser. and (2) Onagra chrysantha Spach, 

 which is composed of O. muricata L., O. parz'iflora L., 

 O. cruciata Nutt. and of a Var. latifolia with which I am 

 not familiar. 



I think it is legitimate to conclude from this that the 

 original Oenothera biennis has given rise to the remain- 

 ing species mairfly along three lines: 1st by an increase 

 in the size of the flowers {Lamarckiana), 2d by a de- 

 crease in this size {chrysantha) and 3d without any 

 change in it. The other features of the flowers are 

 closely correlated with its size and, in fact, appear in 

 great measure to be determined by it. 



The species of Onagra differ from one another not 

 only in the structure of the flowers but in that of the 

 leaves as well. Furthermore the fruits of 0. parz'iflora 

 split by 8 apical valves instead of 4, whilst O. Lamarck- 

 iana has an entirely different appearance. Further, less 



