Oenothera Nanclla. 363 



The dwarfs can be recognized not only as early as 

 the rosette stage but even when the first leaf is developed 

 (Fig. 7^ A). This first leaf is broader and has a broader 

 base and a much shorter petiole than that of 0. La- 

 inarckiana. The same is true of the second leaf. The 

 result of this is a compact appearance in the young plant 

 which makes it possible to record them in the seed pans, 

 if the seeds have been sown so far apart that the seed- 

 lings only just touch one another. Of course there are 

 often one or two doubtful individuals left over, as for 

 example when the seedlings are crowded together in 

 groups ; but the doubt can always be removed by growing 

 the plants in question a few stages further. 



The stage we have just described is followed by an 

 atavistic period. The dwarf characters disappear and 

 it looks as if the little plants aspired to become tall La- 

 marckianas. There appear two, three, or four narrow 

 leaves set on long petioles (Fig. 7SB, v. v. v.); they 

 conceal the two first leaves which are much smaller, and 

 so determine the general appearance of the plant for a 

 short time. But this stage is soon shown to be a transi- 

 tory one by the appearance, in the center of these leaves, 

 of the compact rosette of the regular dwarf type. (Fig. 

 78 B, and Fig. 79 A). 



This so-called atavistic period is very common in 

 seedlings.^ We are all acquainted with the fact that 

 seedlings of species of Acacia with phyllodes have pin- 

 nate and doubly pinnate leaves ; a fact which enables 

 us to derive the species in question from doubly-pinnate 

 ancestors. The seedlings of Ulex, Sarothaninus and 

 those Papilionaceae which lack, or have rudimentary, fo- 



^ See the excellent summary of these phenomena in Goebel's 

 Organographie, I, 1898, pp. 121-151. 



