THE MUTATION THEORY 



349 



in the narrower sense of the word, as previously given. The second 

 and third heads indicate the real progressive elementary species, first 

 those which are as strong as the parent-species, and secondly a group 

 of weaker types, apparently not destined to be successful. Under 

 the fourth head I shall include some inconstant forms, and under 

 the last head those that are organically incomplete. 



Of varieties with a negative attribute, or real retrograde varieties, 

 I have found three, all of them in a flowering condition in the field. 

 I have given them the names of laevifolia, brevistylis and nannella. 



The laevifolia, or smooth-leaved variety, was one of the very first 

 deviating types found in the original field. This was in the summer 

 of 1887, seventeen years ago. It formed a little group of plants grow- 

 ing at some distance from the main body, in the same field. I found 

 some rosettes and some flowering stems and sowed some seed in the 

 fall. The variety has been quite constant in the field, neither increas- 

 ing in number of individual plants nor changing its place, though now 

 closely surrounded by other lamarckianas. In my garden it has 

 proved to be constant from seed, never reverting to the original 

 lamarckiana, provided intercrossing was excluded. 



It is chiefly distinguished from Lamarck's evening-primrose by its 

 smooth leaves, as the name indicates. The leaves of the original 

 form show numerous sinuosities in their blades, not at the edge, but 

 anywhere between the veins. The blade shows numbers of convexi- 

 ties on either surface, the whole surface being undulated in this 

 manner; it lacks also the brightness of the ordinary evening-primrose 

 or Oenothera biennis. 



These undulations are lacking or at least very rare on the leaves 

 of the new laevifolia. Ordinarily they are wholly wanting, but at 

 times single leaves with slight manifestations of this character may 

 make their appearance. They warn us that the capacity for such 

 sinuosities is not wholly lost, but only lies dormant in the new variety. 

 It is reduced to a latent state, exactly as are the apparently lost 

 characters of so many ordinary horticultural varieties. 



Lacking the undulations, the laevifolia-leaves are smooth and 

 bright. They are a little narrower and more slender than those of 

 the lamarckiana. The convexities and concavities of leaves are a 

 useful character in dry seasons, but during wet summers, such as those 

 of the last few years, they must be considered as very harmful, as they 

 retain some of the water which falls on the plants, prolonging the 

 action of the water on the leaves. This is considered by some writers 



