312 Origin of Each Species Considered Separately. 



is generally supposed. They belong to the same category 

 as Delpino^s subvariations.^ 



These crumples occur in many other plants. They are 

 sometimes regarded as useful adaptations. "The more 

 the form of the leaf surface is adapted for retaining 

 water resulting from rain or thaw by trough- or cup- 

 shaped depressions in its surface," says Von Rumker,^ 



Fig. 59. Oenothera laevifolia. Flowers with narrow petals ; 

 a, seen from the side; b, seen from above; c and d, iso- 

 lated petals spread out. In a one of the petals has been 

 removed, a, c, d taken in 1894, b> i" 1899. 



"the longer can the plant keep the water for its own 



use." How far O. laevifolia is inferior to other Evening 



Primroses from its lacking these depressions is not an 



easy question to answer; but this much is certain that I 



have always found it weaker and smaller than the parent 



species. In the experimental garden however where the 



\ The deviations from the type of leaf, characteristic of the 

 species, which often occur at the bottom of branches are classified 

 by Delpino as subvariations. See Delpino, Teoria generate delta 

 Fillotassi, 1883. They are often of an atavistic natuir 



^VoN RiJMKER^ Zuckerruhensiichtung, 1894, P- 6. 



